In reply to RobSamuel:
Cheyne wears, the boulder beach below the neddy fields bouldering area is where the easiest access is, and where I suggest you head for starters for this area. There has been an amount of new routes bolted in the recent past, and basically there is little above 6c. So plenty of 6as etc.
The fallen down area is further north of this, and offers harder routes, and probably has a bird ban too. You'll do well to get to here, let alone climb.
I used to enjoy going to cheyne in the morning and around lunch heading over to blacknor for the afternoon sun. Bigger groups are harder to organise for this. But it is worth the effort and sunshine on a spring day.
If you are all done and sunset is yet to come, then clichéd and touristy though it is, the cove public house on Chesil beach (that's on portland at the bottom of the one way system) is a magical place to finish off the day.