From what I hear, the Coronado Islands are somewhat underwhelming.
If I were you, I'd strongly consider one of three things:
1. A trip out to the Catalina Dive Park
2. A boat out to Catalina (likely three dives at various sites off a boat)
3. A boat out to Anacapa / Santa Cruz (out of Ventura Harbor) off either the Peace or the Spectre (three to four dives at various sites -- possibly including diving with a ton of sea lions!)
If you're feeling adventurous and can find some local buddies whose schedules match up with yours, you could consider shore diving (we do have some nice shore diving from San Diego up to Ventura), but the vis will not be as nice as it will be out at the islands....plus, you'd have to deal with surf.