I haven't stayed anywhere in Tulum, but we visited the area on Monday for sight-seeing, and it's fantastic! We are planning our wedding in Playa, but I fell in love with the relaxed beach-bum vibe in strip of boutique hotels about 15-20 min. away from Dreams-Tulum. I almost wish we were getting married in Tulum instead! I don't know any pricing details, but one place we actually went inside of is called Las Ranitas. It's a small boutique hotel (as are most in that area), so there is the option to buy out the hotel, if you have enough guests.
For something closer to Cancun, we visited about 8 places total:
#1 recommendation is the Marriott Casa Magna/J.W. Marriott in Cancun (they are adjacent). May not fit your budget target, but it was hands-down the best location in Cancun that we saw.
#2 is Villa del Palmar. This place was fantastic and soooo well priced. If you want high quality, but budget friendly and you don't mind a bit of a drive from the main drag in Cancun, this is your place. The only drawback for us was that it was a bit too out of the way for us (about 15 min. north of Cancun).
#3 are the Real resorts in Cancun-- The Royal Cancun (adults-only) and the Gran Caribe Real (family-friendly). Reasonable rates (all-inclusive), and it's nice that there are the two options adjacent to each other, but the vibe of the place really wasn't for us.
In Playa, check out these:
#1 - Hacienda Tres Rios - We've stayed here; would highly recommend. Major pro is that there is tons to do at the resort (eco park, kayaking, snorkeling, bike tours, adults-only pool available, kids' club, etc.). The 2012 rates are around $179 per person, per night (all-inclusive)
#2 - Omni Puerto Aventuras - Great budget-friendly option offering lots of activities for your guests (such as swimming with dolphins!). The 2012 rates are from $139. Option to buy out the hotel (25 rooms); can do either European Plan (EP) or All-Inclusive (AI).
#3 - Hacienda Real by Encanto - This is a hotel only, not a resort; we've also stayed here. It's in down town Playa del Carmen and is very nice (though nothing fancy). Location is great and it's very reasonable at about $100 per room, per night, EP. So, up to 4 people could split the cost of one room.