It's official. The race sent over a press release and Galen Rupp is running the Houston Half as is Ethiopian Feyisa Lelisa. I don't now how Lelisa could possibly be in any sort of shape as he ran 2:16 (2:15:57) at the Honolulu marathon on December 11th.
Lilesa was 4th in Honolulu though, running with the lead group through 30K, then his 35K split (1:47:42) was still 2:09:50 pace. I also remember reading that he walked the last 100-200m while doing his "X" protest sign; without that maybe he is a minute or two faster.
2:14-15 there isn't so bad. Many years the winning time isn't much quicker. Wilson Kipsang won in 2:12 and Wilson Chebet in 2:15, only a few years back. Unless you mean he can't be recovered enough for a good half, only a month out from a marathon ... that may well be true.
Demelash might be Rupp's biggest challenge though. 26:51 PR last year, 4th at the 10K in Rio (ahead of Rupp and he was the one pushing the pace from 6 laps out), and most importantly ran 59:48 in New Dehli only 6 weeks or so ago (only 4 seconds behind Kipchoge).