It also depends on how much time you want to spend in the garden. One of the major problems with wind is really drying out. So you can grow almost anything even with regular wind, if you are committed to frequent watering, especially in the summer. ( I'm talking daily, sometimes morning AND evening.) Placing plants in larger pots (and plastic as opposed to clay) helps with this. Using larger pots also helps with plants potentially being tipped over or airlifted in especially hard gusts. I like the way clay looks, and it also helps with the weight, so I often put plastic inside of clay.

I'm on the 9th floor, also south facing and so I get slightly more wind than on the ground normally, but it's not a problem except for in the spring when we get a lot of fronts coming through. Many days in March through May we have 15-20 mph winds with gusts to 40. I grow a wide range of plants from roses to herbs to veggies. But I'm a major water hauler.

If you don't want to do this, choose types of shrubs which are shorter or have stout stems, and small waxy leaves or needles as opposed to big floppy juicy leaves. If you are south-facing and really have 6 or more hours of sun you could get a nice range of pines or junipers, like the little round mugho pines. Troll a good local landscape center (not a Mart Depot, though I go there too) to get ideas. My neighbor on the 10th floor grows azaleas.

Herbs from a mediterranean climate, like rosemary, lavender, thyeme, oregano etc also do very well in wind, and they have small waxy leaves that lose less water. But in z5 you will have to winter them inside or replace them every year. If you winter lavender and rosemary inside they can grow to be shrub-sized.

During the winter I spray/paint my perennial shrubs with WiltPruf, which is a clear anti-transpirant solution. I don't know if it's really necessary but it makes me feel better.

Be that as it may, you need some tough-leafed plants near whereever your winds prevail (usually this would be from west to east since the jetstream flows that way) and place accordingly. I've had to do some trial and error in my windy corner but for the moment, I have an 8-year old lilac over there which has done fine and am trying a callicarpa (I wanted it to get the extra sun over there). The callicarpa seems to have much thinner leaves and is attempting to adapt over there so I'm still experimenting with that.

I have had peppers and 'maters over there and the peppers very easily defoliate in high winds. I've even had my tropical hibiscus defoliate in those conditions. Alternately, I have a clematis over there that has done pretty well, although it is set back out of the main wind flow. However my plumies and especially my oleander, seemed to do great along that western side (as long as they are secured). Seems the oleander is an old hat to windy locations being that they are used in Texas and other warm areas along highway medians. In any case, this is where some sort of wind break (maybe even a lattice structure) would help.

An informal Beaufort scale for balcony gardeners (feel free to adapt)--
0: nothing moves on my balcony except the pigeons and aphids
1/2: pages of newspapers/magazines on balcony flip around in a leisurely way
1: newspapers/magazines left on balcony will blow off table
2: newspapers/magazines disappear into next balcony/county (add 1/2 for latter)
3: light patio furniture occasionally tips over (if frequently - add 1/2)
4: light patio furniture occasionally piles up against far side of balcony (ditto)
5: I don't have any patio furniture out there that's not screwed to the floor/made of wrought iron OR I won't let pets/children/small adults out there without signing waivers first.

Veggies and most annuals do fine up to 3 or 4; after that arrange for some windbreak. (Avoid hanging baskets over 2 unless you want lawsuits. It's amazing what repeated tugging wind gusts can do to things you think are firmly fixed. ) Shrubs can live happily in 4-5 if chosen well. If you are not a compulsive gardener, over 4 1/2 plant low-growing succulents or bristlecone pines (in heavy squat boxes). :-)

Zone 4 - 14, heh!

I try and secure as much as I can to the railings, and grow certain plants in tomato stakes. I planted all hibiscuses on one side because they tend to hold up just fine, and like I said, there are plenty of times with 20-30 mph winds during the rain downtown here.

My only other real suggestion is if you are getting plants that will flower, make sure you get things with blooms that last for a day. That way they will constantly be replenishing themselves. A good wind storm will rid your balcony of EVERY single bloom, and it is nice to get several back the next day. My Oleanders will lose every bloom in a heavy storm and take weeks to bloom again, yet the hibiscuses, passion vines, and Morning Glories bloom every day new again.

Good Luck!!!