I recommend using www.eltorobravo.net They are located in Costa Mesa, off of 19th street. Their portions are huge and to feed about 40 people was approx. $200 but easily could of fed 50 w/that amount of food.
They don't make the tacos right at your house if that is what you were looking for, but they do deliver. I found Soho tacos prices too be a little pricey for tacos. IMO.
I highly recommend Taco Chop. We have used them numerous times and they never disappoint. They are by far, the most reasonably priced, always on time, clean, and a big hit with our guests. You get carne asada, chicken and al pastor tacos (grilled fresh), salsa, onions, cilantro, peppers; plus rice and beans. Tons of leftovers and always delicious.
You can reach them at 626-465-6958. Ask for Ronnie.