My parish serves Vigil on Saturday nights, and will serve Vigil for Palm Sunday tomorrow. For a regular Lord's Day Vigil, we'll have 20-30 folks, and around 100 for Liturgy that Sunday. I expect it to be about the same for the Palm Sunday cycle.
For Great Feasts that fall during the week, the Vigil will usually have something like 10 folks, maybe, and the Liturgy may get up to around 20 or so. Also, if it's just Great Vespers and not a full Vigil, it should be about 45 minutes. Maybe more like an hour if there's a Litia.
OCA - Diocese of the South.