Those agaves look like variegated Agave de-meesteriana instead of Agave attenuata... there are actually little nubbin-like spines along the leaf edges of this plant, while attenuata would be completely spineless (including at the tip).

Compare these two photos... the first plant does have a few small teeth along the margins, and the tips are well armed. There are a few other differences.



Whatever the name, those two agaves in your picture look like they're doing really well, especially given they're in containers.