Yes, Manzanitas can be made into bonsai specimens. Keep in mind that all of it major branch work will need to be done in the first few years seeing as since the Mazanita is the 7th hardest hardwood. Once the branches hardened it will take advanced techniques to correct any design issues and possibly to some danger of damaging the branch.

Did you research the species prior to make sure it received the right conditions? There seem to be a number of different sub species, each with slightly different needs. Heres a few links Below. Try looking up the different Manzanita's on this botanical sight to help find out what type would be best suited for you.

I would also recommend researching Bonsai in general to get down all the beginner basics (if you haven't already done so). Your local library should have a number of good Bonsai books.

http://en.wikipedia.org/wiki/Manzanita

Here is a link that might be useful: Botanical Index

I would say that most Manzanita will not tolerate indoor conditions.
All the Manzanita that grow here are hardy to at least a zone 7 (if not colder).
Are you thinking it must be brought in because of the smaller container?

There are many ways to protect the roots in the container outdoors.

Josh

Because of the cold and because we also sometime get non-stop rain in torrents.

The tree must have a cold dormancy, with out this a tree may live a few years but will steadily decrease in health and vigor until it goes into a self induced dormancy 9if it even lives that long) and will usually not come out of it and die. A safe dormant period is easy to care for and extra protection can be given by placing the tree (mulched in) in a container or wooden box outdoors in an already protected area. You could also preferably keep it in an unheated garage or basement which is what I do. You can then also keep more sensitive trees than allowed by your zone since you can use a heater to keep the temps at a cold but steady temperature when needed. If you wanted to go a step further you could do both.

If you are having a soil moisture issue due to unusual or consistent heavy down pour of rain you can simply remove the tree from the open, placing it in a mostly protected area out of the rain.