Peoria Sports Complex is home to the SD Padres and the Seattle Mariners. It is a very nice stadium in Arizona's collection of Spring Training venues. Nice layout, good area of town, and with lawn tickets at only $6 it's a deal that is hard to beat. Like most of the other stadiums, the parking is $5 and it is fairly easy to get into and park. I deduct a star because the lawn area in left field isn't too great since there isn't enough slope and can make it hard to see over the fence and other people's heads, plus there is a lack of shaded seats in the stands. Other than that, this is a Spring Training facility I definitely recommend. It is worth the trip from anywhere in the valley.
Tip: Not positive, but you may be able to park across the street in the huge shopping area with all of the restaurants.