Reco's for Catering around Santa Barbara - fish tacos?
Crocodile does catering and are in contention for some of the best fish tacos in Santa Barbara. http://www.treeinns.com/pages/catering.php
Las Aves does catering and fish tacos as well but is more Mexican. "Affordable" can mean a lot of things. There as lots of private caterers also - one person operations with serving staff. http://santabarbara.com/dining/catering/
A very old stand-by is the Jolly Brothers Catering -they use one of the recreation center kitchens which keeps their prices down - every party I went to years ago where they catered always had great food. Surprised they are still around but I would definitely see what the can offer to give you a base line. http://jollybros.com/about.html