There are two ferries from Corozal to San Pedro. The Lady Lowe leaves from the pier between Tony's and Corozal Bay Inn at the south end of Corozal, and Thunderboat leaves from the Reunion pier which is north of there, in town. Corozal is a small town -- just ask anybody you see for directions.
It takes maybe an hour and a half from Corozal to San Pedro.
For hotels in your price range in San Pedro Town, you don't have many choices -- Ruby's, San Pedrano, Tomas, Martha's. Of these, Ruby's is the best.
Belize books and publications by Lan Sluder:
Belize First Magazine http://www.belizefirst.com/
Fodor's Belize and Guatemala Guide
Belize First Guide to Mainland Belize
Adapter Kit: Belize
Fodor's UpClose Central America
Belize Book of Lists 2000
San Pedro Cool (coming soon)