In answer to the--well, my--question, we went to Avec Saturday night at 6:30PM hoping to avoid a serious wait. And we mostly did. Prior to our arrival, we called at 5:30 and 6 to see the status of things--in both cases, the hostess assured us we could sit right down. But we were a party of three, and when we arrived at siete menos trenta, we did have to wait twenty minutes so that a corner spot could open, such that the third person would be slotted in the exit row of the long tables; however, parties of two who came at the same time were seated at the bar immediately and at tables within five minutes, and continued to be seated relatively quickly until about 7:15.
So, if you hit Avec at, say, 6PM, you could be in and out and on to TVH before it gets crowded as well.
Two notes:
1) This was my first time at Avec in a party of more than two, and I do not recommend it if you want to avoid some serious waiting. Case in point: there was a party of three that got to the restaurant about 10-15 minutes after us but who didn't get seated until we were eating dessert--so they had a wait of 45 minutes to an hour. I can only presume the waits for 3+ got subsequently longer as the evening progressed.
2) This was my first flawed dinner here, as oversalting was an issue on the trout--which was tasty--and the pork shoulder. It would be too presumptuous to make causal links from a single not-perfect visit, but my best meals here have been when Koren was behind the stove; last night, however, she was hanging out at Blackbird or running dessert out.