Hi Super Kitty, try craigslist yucatan or andale.mx for apartments, and you can also reach out to Gabby Waldert over at Playa Rentals. Just google her and you'll find her site.
There is a section of this forum called Peep Stuff. That's where you can meet others and plan outings, dinners, beach days, etc. And hey, there are lots of Americans, British, and Europeans who are very nice too!