I love Playa del Carmen,
The travel agent we are using is Teresa from Wright Travel Agency, she is awesome. I have tried shopping around for travel agents, but Teresa really gave us the best rates and she responds ASAP and she is very nice. I only wish that we could make online payments.
As far as resorts we stayed at Riu Palace Riviera Maya. I loved the resort, except that all our stuff smelled like mildew and we had trouble sleeping because our sheets felt damp. We stayed in December. We saw a few weddings at their Gazebo. I will say I did not see any beach weddings and I do not like their wedding locations. The gazebo is located outside of the gym/spa and right next to the pool. The pool is full of activities for the resort guests with a DJ so it is very loud. If you want something quieter, I am not sure where you could have the ceremony. Their back up for bad weather is the "terrace" where you eat during breakfast and buffet meals, it's cool if you understand that the drink machine will be in your pictures. I like this resort for vacation, but a wedding not so much.
We do LOVE the look of Riu Palace Mexico, I am not sure where the wedding locations are.
In 2 weeks we will be staying at the Reef Coco Beach, there is also a Reef Playacar.
We originally had our wedding booked for Playacar Palace and transferred to Moon Palace Cancun. Playacar Palace is a beautiful resort and the Palace resorts have great group benefits.
We also considered, Now Jade, Now Saphire, Sandos Playacar, but honestly once we found Palace we stopped looking.
I will say there is a bunch of great info on this site, if you go through all the posts you can find pictures and great info.
Hope this helps.