Short answers are no and yes, respectively ;-)
Outside of hatchlings, chameleons in general don't tolerate each other well. Some folks are successful housing subadult and adult females in the same enclousure, but it varies. Some species even tolerate 1.1, 1.2, etc. male.female cohabitation, but most species do not tolerate this very well, and in the cases where it seems to work it is usually only in very large, well-planted cages. Adult males of most species are very hostile towards each other and merely being able to see another male (i.e., 25+ ft and line of sight) is enough to stress the two males out. Except in unusual circumstances, most chameleons are best housed individually past a few months of age.
For the cage you're talking about, one individual is going to be most appropriate. There are lots of smaller to medium sized species that could potentially work well as adults in the size cage you have, including Carpets (Furcifer lateralis lateralis) or 'Giant Carpets' (F. lateralis major). Keep in mind, however, that wild caught chameleons often come in rough shape, including significant parasite loads, and may require vet care, which can get pricey. Captive bred chams normally won't have these problems. Hence, a cb chameleon in the $100-200 range could end up being substantially cheaper than a wild caught of the same species in the $50-100 range when vet care is included. A cheap wild caught cham can end up costing hundreds when all is said and done.
As for climbing: almost all chameleons are arboreal, outside of the Brookesia spp., and even they get up off the leaf litter quite a lot. Any species you are likely to choose is going to be a bush/shrub/tree dweller.
cj