Two geese are better than one -- they keep each other company, entertain each other, gossip together, and take turns watching each others' back when they are sleeping . . . plus, a lonely goose is a loud, depressed, lonely bird that is stressed when you aren't able to be around them. If you spend enough time with the birds, even a group of geese can be social and friendly and enjoy hanging out with you outside whenever you are able to spare a few minutes.
American Buff and Pilgrims are on the list as some of the more friendly breeds and are usually easier to find. I think Chinese geese are more territorial in general and are often used as "alarm" geese so they might not suit your purposes. I love my American Buffs also . . . . but everyone loves their breed best! Metzer's hatchery has a good comparison of sizes/weights and temperaments of the most common breeds.
Heat is hard on all geese due to their insulating down feathers -- if you give them plenty of water (kiddie swimming pools) and lots of shade, warm weather should be tolerated for awhile. Extreme long term hot temperatures can really stress the birds out though . . .
