Mehow: I don't own a DT but do a search in this forum: there've been long discussions about them, overwhelmingly positive. I don't know of any source other than direct from the manufacturer, however, with folders you often either have to settle for what your LBS carries or mail order.
Your challenge in finding a Raleigh 20 is not that So-Cal likes cars. It's that So-Cal is far, far from Nottingham England where you'll likely find the highest density of Raleighs.
Same in my city, Ottawa, Canada - and we have EXCELLENT public transportation. If you want a 20, you may have to bid on something from overseas...but then, the shipping jacks that price way up. :\
On the note of suspension: on 20" wheels, the short-throw suspension typical on folders doesn't share a lot in common with what's found on downhill/mountain bikes.
It's function is to make the feel of the small wheels more like larger ones. In my experience with a full-suspension KHS, that's exactly what it does. (sort of the difference between riding with 120psi and 75psi tires over a bumpy road, if that makes sense)
FWIW, you can always take the suspension fork off and put an inexpensive straight fork on. I imagine a short ride on garbage day would net you a BMX fork left by the curb, bike-et-al.
Dahon componentry ranges from entry level to mid-high-end. The DT seems to be good, mid-range componentry that should last. It's not el-stinko nor is it Dura-Ace.
Others will have to give you feedback on their own DT's but the frames seem solid. One owner posted a link to a video of them riding down a flight of stairs on their DT VIII FS. (!)