In reply to EmSB:
I live on Portland. Your questions are wide-ranging and I'm afraid I don't know the answers to most of them. It might help if you gave an indication of how many days you were coming down for and what grade range you're looking at.
What I do know is that, irrespective of grade, at this time of the year, weather dictates that usually it's The Cuttings. If it's sunny and not windy, you can have 'summer days' on Blacknor Central and South. I wouldn't be rushing to Wallsend yet though.
If you've got the latest Rockfax, there are lots of little 'bijou' crags, The Bower, The Veranda, The Nook, etc. The glory of Portland is the big stuff on the West. But the little stuff means that, unless it's pouring down, you can usually get something done.
Look at the windsock at Ferrybridge and climb on the non-windy side of the island.
Mick