Whatever you use, I would stick with a clean sans-serif because it's more readable in small sizes. Probably Arial or Helvetica, to make sure they are compatible across most devices.

Clean typefaces are your best option. Sans-serif is ideal, and I would not even experiment with script typefaces. Download WebOS, Apple, Android, etc. SDK's from their web site, as they all have emulators. Create a simple web page mobile optimized with different typefaces and see which one looks best.