The 'rebar' frame Dahon 26" bikes work well , the old style (pre 2008) Matrix, and the Jack. They fold, but are not really portable when folded, but they do fit in the back of a car easily.
The Matrix 2009/2010 has the 'lockjaw' frame - needs an allen key to lock together, the previous one didn't. Both the rebar Jack (see pic) and the Matrix have Joe Murray designed frames, and are great allrounders. The Jack comes in two flavours for 2010 - D7 with seven gears and the D24 with 24. The Matrix is similar, 24 gears, but with cable disc brakes, and lockable shock forks.
I had a 2007 Matrix - used it as you described, with no problems. Out of choice of the Dahon 26" bikes the pre-lockjaw folding hinge seems to be preferred for regular folding on here, and now the Jack comes with 24 gears the choice is less clear cut. It's down to whether you want front suspension or not. A D24 Jack would do the job well if you like the look of the bike and the spec. Dahon have put Big Apple Tyres on the bikes for this year, a better choice would be a mild knobbly for the front at least if you're playing in the dirt. Otherwise you'll find you don't got no way of stopping in the mud.
I kept my Matrix for three years, nothing broke, the frame didn't squeak, the spokes didn't break, and I used it mainly on the old railway line around here. It sold for almost what I paid for it. A recommendation, then.
At the top of the 26" range is MTB Dahon Flo, but I know nothing about it. Here's the Jack D24: The large size will fit you, but the frames have that compact & nimble 'off-road' design and some taller people think they feel small. The seat to crank distance seems OK for most though.
For checked luggage, the 26" folders fit into large cases, or the Dahon Airporter bag. If you're thinking 20" wheels, and you're doing any lengthy non-tarmac stuff the ride is exceptionally bumpy. Which means suspension like the Jetstream, which does get used as a pocket off-road tourer.
A folded 26" bike is going to fill the trunk of your Camry though.