Brahea is a genus of fan palms from Mexico and Central America. Some are quite small while others are moderate size to large. They fall into several different groups.
A couple species are small and very xeric. B. decumbens and B. moorei are native to cool oak forests and do not grow an upright trunk. Some forms of B. dulcis may also be small and may form suckers.
The following species are larger and also quite xeric: B. armata, B. bella, B. brandeegei, B. clara and larger forms of B. dulcis. B. armata is the well known Blue Hesper Palm with stunning silvery blue fronds and flowers that extend well beyond the leaves. It can handle very cold temperatures in dry climates. B. clara is basically similar to B. armata, but with weeping fan segment tips. B. brandeegei is the largest species, common in parts of western Mexico where it may reach a height of 120'. These species and the preceeding smaller species should all be given perfect drainage, such as a gravelly site or cactus garden, for the best chance of success in our rainy climate.
Brahea edulis is native to Guadalupe Island. It will grow in normal soil in our climate, and also does very well in cool weather. However, it is not really hardy enough to survive Arctic Blasts, and should only be tried in sheltered microclimates, and/or with protection. B. edulis is less hardy to cold than B. armata, though B. armata requires more hot dry weather to thrive. B. nitida is also supposed to be quite hardy and perhaps does not require special xeric soil conditions to perform well.
Many of these species of Brahea are not well known in cultivation. This genus is greatly underrated in my estimation, as there are some species that are likely to be successful in the Pacific Northwest. It might even be worth trying some of the hardiest xeric species in a very sheltered microclimate east of the Cascades. Unfortunately, most of these species are difficult to find in nurseries, besides B. armata and B. edulis.
I would rank Brahea hardiness roughly (VERY roughly, since it is not well known) as follows:
B. moorei: -14°C/7°F
B. decumbens: -12°C/10°F if dry
B. bella: -12°C/10°F if dry
B. nitida: not sure, but supposed to be very hardy.
B. armata: -11°C/12°F if dry
B. dulcis: varies, best if dry
B. edulis: -8°C/17°F
B. clara: -8°C/17°F if dry (not sure about this one)
B. brandeegei: -7°C/19°F if dry
B. aculeata: not sure, perhaps as hardy as B. armata, best if dry
B. elegans: not sure
B. pima: not sure, but likely to be on the tender side.
B. salvadorensis: not sure, but probably also fairly tender.