In general, there are two rings for a presidential TFR, one that is 8-10nm and one that is 30nm.
The small ring pretty much shuts you down unless you are scheduled 121/135. Often that ring either literally moves with the president if he's driving or it pops up in different locations depending on where he is at different times.
The 30 nm ring is usually there the whole time and seems like it's mostly just to keep loitering VFRs away. You can expect to be sent right through it if you are IFR. If you are VFR, you can expect to be allowed through it if you are departing from or arriving to an airport within the boundary of the airspace, and sometimes they will allow VFR transitions as well.
If you are talking about getting into or leaving PSM, it looks like you'll be shut down from just before noon until just after 4 tomorrow (Tuesday). As always, read the TFR because they are all a bit different, and FSS will have the most up to date information.