Hmmmm.....Valley Creek is a no-brainer, since you'll be minutes away. It's a narrow stream, and while there are lots of trout, they're all native. Not an easy bunch to fool! I lived in Valley Forge until late 2006, and saw many a fly angler ready to tear their hair out trying to catch trout on Valley Creek. It can be done, however. There are several other stocked trout streams in the Collegeville area, but I never fished for stocked trout until Christmas Eve day 2006, so I'm not familiar with them. The Schuylkill River is nearby, and the smallmouth should be taking Clousers by mid May. One of my favorite spots on that river was at the Pawlings Road bridge: Pawlings Road GPS - Schuylkill River Trail
That bridge has parking for Valley Forge National Park on one side, and that just happens to be where some of the best smallmouth fishing is. Fish both upstream and downstream of the bridge, about 1/2 mile on either side. LOTS of great fishing to be found there.
As you can see from the map on the link above, Perkomen Creek is nearby. It's stocked with trout, and just a few minutes from Collegeville as well. If you have the time, the Little Lehigh Creek is less than an hour away, and the fly fishing section has plenty of native trout. It's stocked as well, and the Little Lehigh Hatchery is less than 100 yards from the banks of the stream. Heavy rains dump lots more trout into the fly fishing section, making it much easier to fish than Valley Creek. The water is generally gin clear, and trout are everywhere. Well worth the trip if you want to be certain to catch fish, and the surrounding area is very scenic as well. If you've never been to Cabelas, there's a retail location 20 minutes from the Little Lehigh.
I'm not into long drives to go fishing, so I've never fished the other famous streams in Pennsylvania. I've never been more than one hour from fantastic fishing, and usually less than 15 minutes, so that's had a huge influence on my decision to fish as local as possible.
The Delaware River is once again less than 15 minutes away, and that provides all the warmwater action anyone could want. The PA Fish & Boat Commission stocks the Delaware with striped bass, and they can be caught swimming up the smaller creeks that feed into the Delaware! Southeast PA is a great place to go fishing.