I was thinking on doing the same thing. My dates in the area 3/29 - 4/9.
I was thinking it would be fun and try and catch the Angels opener or one of the next 2 games after that. I keep checking to see if the single game tickets are available yet. Any one here know when that happens?
I did find bus route maps at octa dot net (won't let me post link until post count 10)
The one I would catch is route number 50 as I am staying at the Extended Stayamerica.
Yep, #50 is the right one. Note that the closest stop to the stadium will require you to walk through a tunnel underneath the Amtrak station. It's easy, but not obvious how to get there from the bus stop. There is an inset map of the walking route from the bus stop at Katella & Howell: http://www.octa.net/pdf/pdf/dec08/route050.pdf