San Carlos is a very worthwhile trip. We lead trips there several times a year and I believe that it is perfect for low hour divers. Do your best to get out to Seal Island, best visibility and the Sea lions are a blast. A good warm up dive is off of the shore in Lalo cove, not too deep and it is protected. April is a little early for the best temps and visibilty, although the southwest is having a very warm spring. You can check with Desert Divers out of Tucson Arizona, they run a boat(Ocean Spirit, the best boat in the area in my opinion) out of San Carlos and they can also rent you gear. We have a trip going with them the last weekend of April with a day of kayak diving @ Lalo and two days on their boat. Let me know if you have any other questions, I have been diving there for almost 20 years and run several trips a year there without any major problems. Pete