While the west coast of the USA may have a more consistent swell for surfing, I believe the east coast has a clear advantage when kite surfing the waves because the region has a more consistent wind.
The North Carolina coast is a great place to plan your wave riding vacation, accessible areas for down winders and warmer (relative to the west) water temperatures. This article will discuss factors to consider when choosing the right time of year to visit.
For the advanced rider the best time of year would be in the late summer/early fall (September-November) when the Atlantic Ocean is subject to hurricane ground swell and frontal high-speed winds. The waves can be overhead to double overhead.
You will want to bring the smaller kites in your quiver, and also pack a leash for the bigger days. Be sure to check your equipment for any damages before riding in the ocean, and I would advise wearing bright colors, and possibly have some type of pfd on your body in case you have to fully release the kite.
For the beginner rider who is stoked to get some wave riding experience, I would suggest to travel to the coast of NC in the mid-summer time (late may - early July). The afternoons usually have a thermal wind where you can ride with your mid-size or larger kite in your quiver. The summer time waves are generated mostly by wind swell which means they will be a manageable size for the beginner.
Most of the coastline in NC has a road running adjacent to the shoreline with public parking lots. This is a great set up for ocean riding because it allows the rider to park a shuttle vehicle and do a downwinder. I have also hitchhiked in all along the NC coast and I always get picked up quickly and have a friendly driver. Use your best judgement, obviously, but I have only had positive experiences.