If you have to choose one of those companies, I would go for Care, I worked there before becoming a medic and it was pretty good, even though the pay does suck(common to all ambos out this way). Also, FYI, Shoreline has the Westminster 911 contract, that one is weird because the ambulances are OCFA and you are in house with fire, but it is private employees on the box. Also, Schaefer has offices in Costa Mesa and in Pomona. Honestly, being an EMT in OC and to a lesser extent in LA affords you very little in the way of experience. Unless you run consistently with the same ALS crew, you will do little more than o2 and vitals, maybe c-spine.