There are plenty of lodges, and guides in the Punta Allen area. Pesca Maya does day trips, and will pick you up at your hotel. I've fished with them twice, and had great guides both times. You could also stay here,http://www.shardon.com/index.html, and the owner can get you hooked up with one of the guides out of Punta Allen. I've been told this is a cheaper way to go. As far as real DIY fishing, the area around the Boca Paila bridge is good, but I believe that area is in the Sian Kaan Bioshpere Reserve, and you would want get a fishing license before heading out. I'm not sure where one would get a license in that area.
Here is a pic of the Boca Paila bridge, and a link to Pesca Maya.
http://www.pescamaya.com/fishing-ascension-bay.html
I will also be in Mexico in november, maybe we can split a boat. Hope this helps.
Duncan