We usually carve the texture over the whole thing, then pocket for the letters, cut the letter separately and glue in. The texture comes exactly to the letters and cuts faster because the cutter doesn't have to pause to go around the letters and deal with all the fiddly bits on the insides of the letters. The letters themselves can be cut with 2d paths that go very quickly. This also allows you to use thinner (cheaper) material for the backing and have the letters stick out as much as you want.
D&S Artistic Woodworking http://www.dsartisticwood.com