A Mediterranean tortoise would probably be ideal, such as a marginated, hermanns, or greek. I would recommend buying a hatchling to start with, as imported adults tend to be lousy pets and prone to illness and death (hence my recommendation against russians, though if you can find a hatchling or captive raised animal, such would also be great). Before my herd of sulcatas forced me to sell my lot of marginateds, I kept them outside year round in South Texas on all but the coldest of days. Should it drop below fifty degrees for prolonged period, I would recommend bringing them inside. Keeping mediterraneans keeps with it the disadvantage of having to hibernate the animals in as safe a condition as possible, and I generally use refridgerator hibernation techniques. The plus side to this is that your maintenance is reduced to a simple daily temperature check for two months, with weekly checks on weight. I also do not hibernate juveniles until they are at least three years of age. Keep in mind hatchlings are more sensitive than adults to temperature change. Keeping tortoises is not easy, especially if you are outside their natural bioclimatic range.
T.G.