I find it hard to review the sites independant from the bad travel experience I had. Therefore first of all the circumstances and second of all the experience on site.  
 
I tried to visit Tiwuanaku twice (!) from La Paz by public transport. The first time failed unfortunately. After a nice walk over La Paz cemetery I reached the closeby spot where trufis go to Tiwuanaku when full. It was the Friday before the La Paz Anniversary at about 9 a.m. Some other tourists and locals waited there slready half an hour. The office was closed. After nothing happened for another 30 minutes we decieded to go up to El Alto Terminal Interprovincial. Big mistake not to take the efficient téleferico but a taxi. The taxi driver kicked us out as soon as reaching El Alto as he didn't knew the way to the terminal. The Uber driver afterwards got stuck in the huge markets and some parades in El Alto. Finally we took the téleferico and reached the terminal at about noon. We decided that it's too late to visit the one hour distanced Tiwuanaku now.  
 
One week later we returned to the cementary Trufi office at 08:30 a.m. and it took until 10 a.m. until the trufi was full. Not to mention that I was annoyed by the fact that they explained that the week before there was a reunion that's why they didn't operate but normally they go every day. Without apologizing of course. Then we had the painful 30 minute drive to El Alto where the trufi queued with other cars to get petrol. That's when I was fed up with the company and walked to the Terminal Interprovincial from where I took another Trufi to Tiwuanaku. I reached the site around 12:15 p.m. (it's only a 1 hour drive from El Alto) and joined a Santa Cruz Family with a Spanish speaking guide after confirming that English guides weren't available at this moment and would cost 200 BOB and like this I could share a 150 BOB guided tour with the three headed family. Not to mention the 100 BOB entrance to all related sites that are only once visible with the entrance paid. Bolivians pay 15 BOB. I personally hate these price differences based on nationality even though there are arguments in favor of it. The Spanish speaking guide confirmed she would happily answer questions and make sure I would understand everything by using easy words. I did indeed understand her well but when using topic related vocabulary I was out. Unfortunately it was hard for me to ask questions as she usually ran away and delivered her program on the site as well as responding a bit annoyed when asking something she already explained before and I didn't understand. Also she rather repeated her point than explaining it in other words. Maybe it was because we were in kind of a rush as the family already had booked the trufi back. Finally the walk took us more than 3,5 hours with here and it covered almost all places of the site. Concluding from my experiences I would recommand to take an agency to do the trip from La Paz that includes transport and an English speaking guide or use the trufis from the terminal Interprovincial in El Alto and always go there by teleferico and never by car from La Paz! 
 
I couldn't enjoy the visit as much as under conditions with less of a hassle. Nevertheless I try to share an opinion on the Tiwuanaku site as such. It consists of a main excarvation area with the remains and reconstructions of three different temples. Some original material is used but also replacements and it's in the end ruins. However some pieces are rather fascinating like three monoliths with carvings of a person and many details same as the sungate for the solstices. There is a unique walkway along the area with some signs with little details in English and Spanish. Bring sunscreen and a hat. You can store your bag for the visit at the entrance. Additionally there are two museums closeby that should be merged in the future into one bigger museum. Basically no new excarvations are made because of lack of space in the museums. One museum displays the biggest found monolith with again  many details and nicely displayed in the litoral museo. Also there is a room on Lama related findings in the site. The ceramic museum displays mainly this with some good objects that have survived many centuries in a good condition. There are general infos in Spanish and not many details on when the objects were used. Only technical infos on when and where they were found. Finally there is the site Puma Punka on the other side of the road towards the highway which is a ten minute walk away. This excarvation side appears even more technical and displays single stones lying next to each other that originate from the Tiwuanaku culture. The most interesting one I found was the "H" - stone which was carved in order to put multiple of these together for constructing something.  
 
Finally I tried to see another WHS that day by walking to the UNESCO coordinate of the Qhapaq Ñan position next to the town center. That can not be recommanded as it´s on the grassland of a local family and there is nothing to see. This location is covering a huge area where not necessarily something is visible. The church at the plaza was made by the Spanidards from the Tiwuanaku remains and is therefore interesting to get a look on. 
 
Getting back to La Paz at about 5 p.m. when the sites are closing was easy as trufi drivers drive around town to find there clients. They start 1 quadra south of the plaza. 
 
As mentioned I find it hard to value the site independant from the struggles I had. It feels less touchable and fascinating as other archeological sites like Rapa Nui however it´s still interesting to visit the remains of this culture in this unique Altiplano landscape close to Lake Titicaca.