It seems as if Sempervirens is very much like Semperflorens.
Semperflorens are frequently planted outdoors in the frost free season. There is nothing wrong with that as they tolerate a variety of weather conditons and soil types.
Things are different for Rex begonias. There might be cultivars that tolerate the conditions in your porch, but they are not as tough as Semperflorens. (less tolerant to humidity/temperature fluctuations, irrigation errors, direct sunshine, wind)
Unless someone else can tell you which cultivars are suitable for your climate, you have to try it out.

The plants just say "Begonia Rex Assorted" and they are in 4" pots. I'm disappointed they weren't named as they were sold by a very good nursery.

I took a photo:
{{gwi:430654}}

I guess I will go ahead and try them on the patio. I do not get frost on the patio and there is never full sun in the spot I wanted to grow them. They would actually be very close to the house.

-Melanie-

Good luck then.
You say "very good nursery". Do they have an internet address? If so I would be interested too, as I seem to have bought the same cultivar as the one in the middle of your picture.
It looks very similar to Begonia Rex-Type 'Meteor' on http://www.stbegonias.com/

Here is a link that might be useful: {{gwi:430652}}

The nursery is Matsuda's in Sacramento, CA. I guess I shouldn't say they are "very good", they are just my alternative to big box nurseries and I have bought many nice plants for my yard from them. They often have fancier cultivars (though not for everything) and they grow many plants locally.

Their website is not useful nor is it complete.

I will try the begonias outside and see how they do.

i would think that sacramento would be a great place for begonias in a sheltered outdoor area for at least half of the year. in oregon, i had mine outdoors when the night temperatures were above 55 and kept them out until fall. the ones kept outdoors did fantastic.
some rex cutlivars are more tolerant than others, but they all like humidity. the one on the very right in your picture is a pretty easy one. you'll notice the other two will develop spots if and crisped edges if you let the humidity drop too low. i'm not really familiar with your area, so you may experiment with both clay and plastic pots to see which works better, and requires less monitoring for dryness. i use only glazed clay and plastic.

you can always propagate some leaves so you'll have backups and then experiment with different growing conditions with your original plants.

-ming: i've killed a lot of plants during my "learning process!"

Ming: thanks for your vote of confidence! I still have them sitting on the kitchen counter b/c we've been having light frosts (maybe for a couple hours in the early morning) the past week. I don't think the "begs" are too happy indoors w/the heater. Lots of new leaves appearing but an older leaf on each of the green plant and red plant has flopped off. I'm going to repot them this weekend into a glazed clay pot and set them on a tray of wet pebbles.

I'll try not to feel too bad if they don't make it but it will be awesome if they do!

-Melanie- (who killed a beautiful coral-flowered begonia a few years ago and, subsequently, only grew semperflorens cause they're easy)

I just wanted to share with everyone that I transplanted my three rex into a pot and left them in the sheltered spot on the patio (no humidity tray, yet, since it's still the rainly season). They are all quite happy, no floppy leaves, and appear to have emerging new growth. It's probably still too early to fully assess how they're doing but so far they are still alive. Thank you everyone for your thoughts!