Hi EmmA1025, I'm having my wedding in November 2013 in Mayan Riviera at the Gran Bahia Principe Tulum. The quote that I received from my TA is around $1103/pp (incl. tax) all inclusive from Toronto, Canada. She also quoted Grand Sirenis Riviera Maya for me at around $100 more than the Gran Bahia. However, I believe she mentioned that February-April is still high season for travelling down south, hence why some of the quotes you're getting are slightly higher. I would try end of April or beginning of May 2014. However, come May, it's etching near hurricane season. But those resorts I listed are pretty nice, and I had friends who have stayed at both. So maybe you can start there.
Congratulations on the engagement and happy planning! I got engaged 2 months ago, and finding this website is probably the best thing that's happened to me for planning. Cheers!