I know that it is pretty much in the parking lot of Angels Stadium, so it is not far to DL. I know there are busses that go up and down Katella, but I am not sure where the nearest bus station is. I would imagine it is not far. If you'll have luggage and stuff, it may be easiest to do a taxi, especially since it is not far. But I think a bus maybe your cheapest option. You may also be able to hire a car or someone to pick you up at the train station.
I am sure someone else will know the location of the nearest bus stop. Sorry I wasn't a lot of help