I visited Xochicalco on my Mexican trip in March 2019. Unlike other Mesoamerican WHS, this archaeological site does not stand out for its impressive pyramids or other major constructions. It is rather a well maintained and cohesive ensemble of buildings which forms a complex with a high density of constructions. 

As described by others, I traveled by public bus from Cuernavaca. I first visited the nice museum and then walked to the site. It sits atop a mountain with great vistas on the surrounding valleys. The defensive aspect of this city built in troubled times stand out and, alike previous reviewers, I found it similar to Monte Alban. I had a map of the site (I don't remember if they give it at the museum or the tourism office in Cuernavaca), but the path is well marked and many interpretive boards allow you to understand what you witness. Few buildings stand alone as exceptional (probably only the finely ornate Pirámide de Quetzalcóatl). I asked an adorable Mexican family to take a picture of me in front of this temple and befriend with them. Even thought the rest of the site is not artistically or architecturally jaw-dropping, this site still forms a coherent ensemble. Ball courts, plazas and ruined buildings are to be seen. It is a great half day trip and a pleasant dive in the history of a lesser known civilization.

When I visited in 2019, the observatory was still closed following the 2017 earthquake (alike many buildings in the states of Mexico, Morelos and Guerrero). At around lunch time, I was done with my sightseeing and headed back to the bus stop. The family I befriended with was there eating fruits and they shared lunch and chatted with me while I waited. People working there for the parking watched for buses and told me which one to take.

Cuernavaca is finally a fairly nice city with a WHS monastery (the Cathedral, still closed because of the earthquake). One last place I would recommend in the city is el Salto the San Antón, a beautiful 40-m waterfall located a little west of the center. It is bordered by columnar jointing, an infrequent geological formation in this part of the World.