In reply to Katemonster:
Yosemite! April-May would be perfect.
Royal Arches (5.7) is a super-classic 5.7 with a 10 minute walk-in and abseil descent. There is a load of single pitch cragging with 5 minute walk-ins and great routes - pick up the Supertopo guidebook for details. One I particularly enjoyed was
Bishop's Terrace (5.8). I'm a bit less sure about the length of the walk-in for these (it may be more like 15 minutes), but I would also really recommend
The Grack Center (5.6),
Harry Daley (5.8) and
Central Pillar of Frenzy (5.9). Also the scenery will be wonderful at that time of year with all the waterfalls flowing!
Other areas...
Wall Street in Moab fits your criteria, and also
No match for crag id:3030. If you happen to find yourself in the Pacific Northwest (and I wouldn't recommend it in March-May) then there is a fair bit you could do in Squamish, and there is some excellent granite with a 5 minute flat walk-in at
Index Town Wall.