Just played it a bit here. Surprisingly fun, but then again, I love Breakout style games. You're using a base that is already proven to be fun, so it would be cool to see a new take on the gameplay other than just putting Breakout in a western setting. Although I have to say, there is something awesome about sending a coyote out to kill cacti.
The respawn time is around 3 seconds, but it feels like forever, you should consider cutting that at least by half.
A score or lives system would help too!
...and obviously music, sorry, I can't help you there, but I'm sure you'll find someone soon.