This time of the year up that high you won't get any salmon. There are some trout in the park but it gets hit pretty hard. You will mostly just catch 6-10" fish. However, there are some summer run steelhead in there right now. Fish it really early as it is low and clear. Use small hooks, leader and corkies. Sand shrimp and jigs also work well. The park itself gets hit pretty hard as it easy access. I usually fish from the other side and fish downriver or go above the park and fish the head works. You will most likely see the fish in some of the holes and they will be pretty stingy about biting. Just keep at them and putting your bait right in front of there nose. Sometimes it will take 20-30 casts before they hit. Also, try to stay in the shadows, don't walk in the water or let them see you. Being this low they are real spooky.
Good Luck.