Be sure to frequently test your font selections on your device even if you simply capture a screen grab of it and send it to your mobile. View it in the sun. View it in a dimly lit room. View it in the environment your users will consume it in. Be critical and adjust as necessary.
To that end: Test on real mobile devices without breaking the bank, and try Adobe Shadow, a simple app that connects multiple devices to your computer wirelessly, and instantly updates them as you design with HTML & CSS.