I'll guess that you'll get some responses along the lines of "I weigh as much as/more than you, and I haven't had any problem with a _____".
The thing is, you can probably get away with going significantly over a manufacturer's specified weight limit, but if something does fail, then you may have trouble trying to make a warranty claim. In your price range, you may just have to accept that. It's more likely that you'll break spokes than the frame itself, so that's at least fixable.
In your price range, the Jack, and other low end Dahons, sound reasonable. You could also look at Downtubes. The smaller wheels could actually be stronger.