I guess for you is best way is to start doing it with java and in some time further switch to scala - for example you be able start developing with Play framewo

I guess for you is best way is to start doing it with java and in some time further switch to scala - for example you be able start developing with Play framework which is support both java&scala in one project. RoR/Django is good for prototyping and for fast start, but if you don't know it's it no sense I guess, you will make it more faster with Play/Scala.