Practices are open to the public tomorrow (Friday) through Sunday, from 9:00 - 12:30. According to the Post-Gazette, the practices are divided into two groups, one going at 9:00 and the other at 11:30. In between the two sessions, at 10:00, they groups will scrimmage against each other.
I wish I could go to see one of the practices - I'd imagine they'll keep Crosby and Malkin in separate groups to let them go up against each other in the scrimmages. That would be fun to watch.
The team will have their first two exhibition games next week, on September 19th and 20th. Both will be on FSN at 6:30. It's the first time a Penguins preseason game has been televised.