For California Adventure, walk across the street in front of Paradise Pier and through the lobby of the Grand Californian. Continue past the pool area; there will be signs pointing the way. As a PPH guest, you are supposed to be allowed to use the GC guests entrance to DCA--they intended this when they closed the PPH entrance. When we stayed last year, we were never refused the use of this entrance, and I verified with PPH that this is still allowed as of two weeks ago. Of course, it seems to me that the CM's can sometimes give conflicting information, so take that with a grain of salt. If they gave me a hard time, I would be nice but ask that they verify their information before they turn me away.
For DL, you have a few choices.
1) You can walk through the Grand Californian. In the lobby, there will be a sign for Downtown Disney pointing left. If you follow those directions, you'll end up in Downtown Disney not far from the entrance plaza, just head to your right.
2) You can go out the back of the PPH and follow the path to the right. This path takes you past the DLH and into Downtown Disney. Walk through Downtown Disney to the main gate.
3) Follow the path behind the PPH to Downtown Disney, but stop at the monorail station, which is next door to the Rainforest Cafe. Ride the monorail to Tomorrowland. This is probably not the quickest option.
Frankly, I like the Paradise Pier. I know that I'm seriously in the minority.