Spell check can be customized/disable via:
Android 1.1.0: File -> Settings (Project Settings […]) -> Inspections -> Spelling -> Typo
Android 4.1.1: File -> Preferences -> Editor -> Inspections -> Proofreading -> Typo
This brings up three options that can be enabled/disabled:
- Process code
- Process literals
- Process comments
Uncheck whichever boxes you would like