Leif,
A few notes on reading your post and some of the replies. If you are new to sailing and boating, I would recommend practicing in Alamitos Bay to get your sea legs ready before venturing out into the semi-protrcted waters behind the break wall. Long Beach has beginner and intermediate sailing classes at Lido sailing center for really cheap and thats a good way to learn while you are working on your boat.
Once your ready for it sailing & boating inside the breakwall is quite nice, the wall blunts the majority of the force from the open ocean swell, leaving just some residual energy, some pointers though;
It can get kinda windy and a bit choppy in the afternoons, nothing unmanagable if you pay attention, morning time is calmer.
Dont get too close to shore or the break wall outside either, stay at least as far out as the end of the pier from shore, about 200 yards, technically you have to stay well clear of the swim line anyways. The wind tends to blow nearly directly onshore and it makes it very hard to tack back out, at least one nice sailboat is grounded on the beach here each year.
Dont get too close to the lee side of the break wall in a larger ocean swell either, it creates small backswash / eddies that can suck you back onto the rocks.
It is best to stay as far away from the large ships as possible, especially out to sea, they are travelling much fast than they look and it may be better to slow down and go well behind them if in doubt. They are going much slower entering and exiting the harbor, but take caution crossing the queens gate and the cabrillo gate where they enter and exit the harbor. Additionally bewear of other motor boats, they usually dont follow the rules and are careless.
Outside the breakwall I dont have much help to offer you, usually we dont have that big of waves, the swells are usually long period so not to bad, but tacking could be hard. Just use common sense, if in doubt, dont go out.
PS if you need a sailing partner I would be happy go with you and to learn more, I have been eyeing the Northeaster and Southwester for similar goals for a couple of years not.