The town is not that big, so you can easyly walk around.
For heading south to the mountains, use Blvd des Perolles and walk to the very end, where the 2 streets come together. After the roundabout is a good spot.
Heading east/west on motorway: catch a bus to the beginning of the motorway (Fribourg Nord) and try to hitchhike from there. Theres another drive-in of the motorway (Fribourg Süd) which you should prefer. Catch a trolley bus in the other direction (Villars) to the old "Jumbo" - much more traffic there but the spot is not great. To get in to the motorway, cars have to turn right at the roundabout and then the freeway just starts...