The cold tolerance chart is interesting. Even for my zone 8a, I think the only really good candidates would be those agaves with cold tolerances below 0F. A few years ago, those with a cold tolerance of 0-5F would be fairly safe bets. Not so sure now since in the last 5 years records have been set and the temps have fallen below zeroF. Last winter, which was pretty mild for the most part, had 36 hours that stayed below 0F. The plumbing companies were happy, I guess.
Historically we haven't seen temps that cold and even single digit F temps are not common. There are agaves that live here. I have one growing at the hunter's camp in the pasture. Something chews on it all the time, so it's very unattractive. I have tried unsuccessfully to move offsets (it pups aggressively) here at the house, but the soil is very different from that in the river bottom where the camp is. I see established agaves driving around, but some of those were clearly badly damaged by the cold spells. Some really large, established plants melted in the spell last winter. Problem for me is I don't know the specific identity of the agaves I see. I'm doubtful all the offerings I see at the nurseries can be trusted. Some of those offer some plants as landscape plants that I know definitively won't survive a winter here.
There's a large, long established and beautiful blue/green speciman growing in the edge of Abilene on a busy street that I note when I drive over there. I've seen no evidence of offsets in the 3-4 years of observation, but it has weathered the temperature drops in winter undamaged.
