On Android 4.x an older version is implemented but on Android 4.4 it should work without plugins. I use a polyfill for iOS and Android which actually uses websql. The polyfill adds the indexedDB API while I isn't actually supported and converts the calls to websql!
websql is supported on android 2+. See the indexedDBShim for details: https://github.com/axemclion/IndexedDBShim/
Note: The polyfill isn't perfect, not all methods support an IDDBKeyRange but you can workaround it in most cases. It does workvon iOS 4+ if you want to support iOS in the future.
Edit: Also the answer your question, you can just open the database by name. There is no need to know the actual location on disk.