Still think the ioverlander.com site could serve as a reference source simply because it already has a heap of RV parks listed - and there is provision for photographs - as many as you like and subsequent visitors can add more, plus comprehensive descriptions plus what facilities are available AND the ability for recent visitors to add their comments AND update the primary listing.
At the moment there are 288 listings for established campgrounds and going down the list, I'd say half or more have "RV" or "Resort" in their name and possibly a lot of the others could be OK for motorhomes. After all, it doesn't take much in the way of facilities to be considered an RV Park in Mexico. Bit of spare ground, couple of wires draped through the trees hooked to outlets nailed to the trunks and water if possible. voila!
IPhone and Android aps are available and selective searches of the database (or the whole lot) can ge downloaded as a GPX file and loaded onto any Garmin so all the info is available OFF_LINE and viewable on a map with all the details available under your index finger. Apps can be set up to update automatically if you want, or do it manually, but either way, what you have available off-line can be right up to the minute.
What other source offers that sort of accessibility. Anyone can log in and supply information or download the files - all at a cost of ZERO.
Granted, some of the info is likely to be out of date, but all that it takes to make it up to date is to check in to that page and update it. Too easy.
Couple of examples
http://app.ioverlander.com/places/125-yax-ha-resorthttp://app.ioverlander.com/places/205-los-coyotes-bahia-de-concepcionhttp://app.ioverlander.com/places/103-rv-park-san-lucas-covehttp://app.ioverlander.com/places/200-kiki-sThis is similar to what you see on your smart phone and touching any symbol brings up whatever details others have provided - OFF-LINE
Did I mention the cost - gratis! Costenlos, libre, free