Funny you should ask this, i've got a week off and i'm actually going to melwood tomorrow for some autographs.
Have been once a few months ago, primarily to get my Xabi Alonso match worn shirt signed, but also took some other stuff to get signed. Be prepared for a lot of waiting around, and quite a bit of disappointment.
When i was there, miraculously Stevie G stopped, along with Jamie Carragher (who by all accounts always stops), Alonso, Kuyt, Sissoko, Zenden, Agger, Gonzalez, Aurelio and Pepe Reina. The rest just drove past.
By all accounts, its rare for Gerrard to stop, and Hyppia never stops, Riise very occasionally, and I've heard Crouch will only sign outside the ground at home games. Rafe is pretty good for signing autographs, but he works stupidly long hours, and to catch him coming out early is a miracle. We gave him an hour after the last player left and still no sign of him.
Due to the whole ebay money making and forgeries, it seems you'll get bettter sigs if you ask them to dedicate to you (although my mate asked Carra to sign to him, and he said I'll sign it, you can write your own name!).
I'd also guess it'll be busy tomorrow, kids holidays should have a fair few younger lot out
If you want to watch them train, a lot of the younger local kids rob peoples bins and stand on those watching over the walls. I'm gonna be in the other half's Freelander, so I'll pop the moon roof out, stand on the seats and watch that way. A lot of white van workers drive by during the day, park up for 10 mins, climb onto their roofs and watch for a while
Hope this helps, if you do go tomorrow, watch out for the bloke in the black Freelander with his head stuck out the roof.....come say hi!