Glaar, you run the risk of making me look like an optimist. We do know that the Marine combat radius spec is all high-altitude - see this chart, old as it is:
F-35KPP20070402.jpg Photo by SpudmanWP | Photobucket
We do know that the F-35B has about the same internal fuel fraction as most other FJ types (around 0.3).
The status of drop tanks has been a little uncertain. They were shown in early briefs but were certainly dropped for the F-35A service-entry configuration around 2007. However, Israel indicated that they wanted tanks, and Elbit's Cyclone subsidiary had a design - but that's gone quiet lately.
There's been no recent visible activity regarding tanks for the F-35B, but FWIW, there is this:
F-35 external fuel tanks.... ? FighterControl ? Home to the Military Aviation Enthusiast