I have seen only 1 honey bee this year working a carrot flower. After that, nothing else. Mostly hover flies, assorted ants and beetles.
I don't really have acreage to talk of but I certainly plant for my bees. Even the few mint plants, mostly weeds, I have seem to effect the honey I have. When harvesting I actually found a patch of light colored honey on a frame that tasted like mint. Of course it's drown out when mixed with everything else they harvested.
Borage, Cosmos, Poppies, Dahlias, Cone flowers, Sunflowers, Clover are all nice plants to have. Not all are appropriate for cover crops but they're all easily found in most nurseries.