What time do the buses in Los Angeles stop running?

I would see what this has to say. It is going to vary depending on what routes you need. Some lines stop running earlier than others.

How do I find out?

http://www.metro.net/around/maps/

Some stop running at 2am. Some stop at 9pm. There isn’t a set time that all bus lines stop running. Use the trip planner above to see what it suggests.

It all depends. Some are 24 hours. If you use maps.google.com

you can plug in your route, and click on the little bus icon. It will give you the best (arguably, sometimes not) route to take.

It will also tell you what time. I lived in LA for two years and I lived by maps.google when bussing it. Their transpo system is awesome.

Also www.metro.net is their official site, and you can call 800-commute is their operator that can help you with any such question.