I wasn't going to comment because the original question concerned marinas between Ventura and Channel Islands, but in light of Jeff's comments I thought I'd weigh in with a few observations, just in case they might prove helpful to what he already said.
I'm located in San Pedro as well, just to the north of where Jeff is, in the portion of the marina named "Holiday Harbor." I like it there very much. Great management, excellent facilities, and quiet. They have a nice club house and put on social events. They threw a great Christmas party for the tenants, free of charge. Plus, as already noted, it's an easy sail to Catalina. And there are vacancies (at least for 30' sips). Highly recommended.
If you wanted a slip in Dana Point for some reason there should be no problem getting one. The Ericson 26 I just bought was in Dana Point and I kept it there for a month while making some mods to it before moving it up to San Pedro. The managment really urged me to stay but there is no way I wanted to. I like San Pedro much, much more than Dana Point. Dana Point is considerably farther to Catalina, the sailing right around the harbor is not as nice, there are tons of kayakers and paddle boarders clogging up the channels, and there is far too much pedestrian traffic around the docks from joggers, roller skaters, bike riders, etc. Plus, the docks are showing their age. I couldn't wait to leave.
The marinas in Long Beach are city run, so think "DMV" in terms of the customer service attitude. Last I heard you would indeed have to be put on a waiting list to get into Alamitos Bay Marina, but I haven't checked lately. Even though both of the Long Beach marinas (Shoreline and Alamitos Bay) are closer to my house than San Pedro is, I'm happy to drive the extra 10 minutes for a much nicer marina. I used to have a 27 footer, both at Shoreline and Alamitos Bay. Never again.
One last comment about San Pedro: I actually prefer the "old" (1986-vintage) marinas vs. the brand new one that was just built in the last year or so. The major problem with the newest one (besides the higher cost) is that some of the slips are a *long way* from the parking lot. I mean a loooooooooooong way!
BTW: All of my comments above about slip availability pertain to 30' slips. I don't know if there are waiting lists at any or all of these marinas for other sizes, but as that's the only size I was interested in it's all I asked about. I should also mention that, although I'm in a 30' slip, I pay for the size of the boat (26') and not the size of the slip. That is a fairly recent development brought about by the number of vacancies the marinas now find that they have on their hands--again, at least in the 30' range.
Cheers,
Alan Gomes
E26-2
San Pedro, CA