James, your climate sounds very similar to mine, except our daytime temperatures in the summer are much higher. We stay above 90F and regularly go above 100F for weeks at a time. I have a Howea seedling in the ground and it is going on its second year. It was originally one of a trio but the other two died when we had a freeze in January 2007. This one survived and has come back nicely. Here is a photo of it i took last month. It is currently opening another frond.

{{gwi:497132}}

Thanks for replying, someone near me is growing a Schefflera Arboricola, and it is really healthy. I also found out that someone also near me is growing bougainvillea glabra. Min. temp this winter in the shade was around -0.8 (over 30F).
Thanks,
James

Regular/normal temperatures will probably not be a problem with any of those tropicals you mentioned as well as the kentia palm, but any unseasonably cold freeze in the winter could potentially damage your tropicalia. I protect my kentia anytime temperatures drop below 30, which i have only had to do a couple of times. I leave a small fan heater next to it overnight to protect it.

About the bougainvillea, i have found that Bougainvillea x Buttiana is more cold tolerant than most of the other bougainvilleas. All of my bougainvilleas experience some stem tip die back in the winter, but the buttiana doesn't even go completely decidious. They come in several different colors. These are all Bougainvillea Buttiana cultivars: Golden Glow, Louis Wathen, Mrs. Butt, Orange King, Temple Fire, and Barbara Karst. Here is a photo of my own Bougainvillea Buttianas. This purple one has just begun to flower:
{{gwi:32376}}
and these newly planted ones are Barbara Karst:
{{gwi:494382}}

I brought back a bougainvillea cutting from the Canary Islands, but I don't think it will last much longer. I hope to plant a strelitzia outside next summer, and I've just planted a cluster of Howea in a sunny part of the garden.

At around the 28f or-2c,Howeas struggle.Even large ones that seem fine will later in spring as temps rise turn to straw colored fronds. The rap is that this is a very slow palm to recover from damage caused by cold temps.I think -2c,-3 every winter is too cold for them.
But,they are worth a try if those tmeps are rare and balanced by nice long summers.Los Angeles with its upper 40's f winter night temps and rare above 90f in summer is the Howea growing mecca of the USA.
In colder areas, If you do get it to size..it would be a real heartbreaker to lose a trunking Howea.