by etherton
I searched the rules forum and couldn't see this question asked this explicitly, so I figured I'd add this for posterity.According to the BGG unofficial FAQ, you are allowed to resolve your dice in any order you choose (not just the order they're described in the rules).
Therefore, if you are not in Tokyo, you can always choose to use your healing dice before you use your attack dice (and run the risk of somebody leaving and forcing you in).
I had gotten confused by the order they're described in the rules and played a game where you could not heal before attacking Tokyo, and it caused a weird meta-game where people low on health were trying to avoid rolling claws so they wouldn't lose their hearts if the player in Tokyo decided to leave. I much prefer the game with "you can heal before you enter Tokyo".
-Dave