Man, a ton of advice non-specific to SoCal.
You can get decent HP fills almost everywhere here. Some shops charge more for a HP fill (>3000psi). Almost no shops charge based on CF (at least for air or nitrox). Almost no shops will overfill LP cylinders.
The VAST majority of our shore dive sites are shallow (biggest exceptions are LJ Shores and Vets, where you can get some real depth). For shore diving at all other sites, 100cf is almost always enough. For Laguna and Malibu dives, that's probably plenty overkill (we often got *two* dives off a single HP100 at some of the sites in those areas). For boat dives, down to 100', it's nice to be able to maximize NDLs on the most common nitrox blend (32%). At 100', you have 30 min of NDL time on 32%. At a not-great breathing rate of 0.75 cf/min/ATA, that's 90cf. Min gas at that depth is about (conservatively) 40cf. Thus to safely maximize NDLs at 100', you'd be best off taking a HP130 (90+40 = 130).
For deeper recreational dives in SoCal, almost everyone I'm diving with (from very small women to large guys) is using HP130s. No one I know (short, tall, skinny, etc) has any trouble trimming them out (this isn't true for the longer HP120s which some shorter divers have a problem with). It's nice to have everyone on the same cylinderes as it makes computing turn pressures a snap (for more aggressive recreational dives). Some of the local boats with compressors can only fill to 3000psi, which means a 130 is still offering you over 100cf even when underfilled to this pressure. 130s overkill for the shallower sites (though have enough gas for two shorter, shallower dives), but very nice for the deeper stuff, especially for someone who might be breathing heavy.
If you stick with the HP130s made by PST or Worthington, they are only -2# empty, the same exact weight as a HP100.
ALL THAT SAID, for a new diver with your dive count (0-24), I wouldn't worry too much yet about the need for tons of gas. No real reason to be diving deep at this point, and your consumption rate is almost surely going to fall (possibly dramatically) as you continue to dive and gain comfort and experience, making the cylinders you use now last longer. If and when you decide you're ready to head deeper or stay longer, then think about stepping up to a bigger steel cylinder.
Have fun!
