Visited this WHS in August 2013. I got there with a private drive from Asuncion to Posadas and from Posadas Argentina Explored the two missions. To my surprise they were very very well preserved. Didn't see that many tourist there and for that I can see they do a good job there compared to many well visited other sites. For me, being from Europe, it was great to see such architecture in the middle of the jungle. WHen I visited they had information in English, and sometimes little English speaking guide. Further it was all well documented with a tourist office which information about the site.

For my full story and photos see here:

www.christravelblog.com/paraguay-asuncion-encarnacion-jesuit-missions-2013-07-31-2013-08-11-s-a-trip/