If you are staying on Caye Caulker it makes no sense to book a fishing trip from San Pedro, they are alot more expensive anyway. There are alot of good fishing guides here. We have been going out with Elloy Badillo for almost 10 yrs now, his family goes back several generations in fishing guides.
Some guides will take you fishing for awhile, then snorkling, then off to catch some lobsters, all will clean and fillet your catch. On average a 5 hour trip is $125 to $175 U.S for the boat, if you have 4 people thatsabout $40. each. Bait and poles are provided.
Parnell is also really good.