Sisteron is a compact and approachable crag, consisting of a large but narrow fin of rock, with slabby, sunny routes on one side, and a few shady, steep routes on the other. The rock quality is excellent, though the slabby routes tend to have cleaner rock than the steep ones. As a destination, it's not extensive enough for a base, but makes a good alternative to Céüse if you're feeling like having an easy day and can't face the walk-in.
The crag mostly faces south although there are a few north-facing hard routes on La Faille. It is exposed to the wind and on cold, windy days can be quite unpleasant. If you're looking to climb on the sunny side, it would be wise to avoid hot days when the place turns into an oven.
If you're killing some time waiting for the sun to go down before you can get on the rock, there is an extensive and popular summer lido in the town.
If you're looking to climb on the steep, shady side, then any time except winter should provide reasonable conditions. It is also worth noting that early in the season, the north-facing wall may be a bit dirty.
Sisteron can be easily accessed from the A51 by exiting either at junction 22 (from the south) or 23 (from the north). The crag is clearly visible from the town; head north on the N85 to the first roundabout, and take the first exit onto the D951, this crosses the river, once on the other side, turn right and drive below the crag until you can reach parking places on the side of the road. Please don't park in the village.