When I first began looking, I had the same reaction also. I think the best thing you can do is contact a villa rental agency and have them do the legwork for you. They're pretty familiar with wedding villas and your requirements. Some of them are: Casa Bay Villas (www.casabayvillas.com: Jennifer Lawrence, the proprieter is very nice), La Punta Realty (www.lapuntarelaty.com: they take some time getting back to you, but have some nice properties), Casa Helga (www.casahelga.com: I didn't particularly care for her attitude), Casa Garza Blanca (very affordable), Vacation Rentals By Owners (www.vrbo.com: allows you to contact the owner directly), Boutique Villas (www.boutiquevillas.com).
When I visited PV for the first time in 2009, I rented thru Casa Bay Villas. She has a ton of info, photos, and can direct you to planners, etc. You probably already came across Casa China Blanca, Villa Mia, and Casa Valerie. Those are the main wedding villas. Think outside PV as well. You can find villas anywhere from Sayulita to Mismaloya. I think those agencies will give you a good starting spot for $20,000. Let me know if you need any other help!