Do you want them flowering wet season or dry season?

Ian, I'm just below Brisbane in Australia, around 28' south - only sub-tropical. How does your location compare?

I really don't mind when they flower. Alison, our climate would be almost identical to yours. We are exactly on the tropic but our house is nearly 900 meters above sea level, so we do get a "winter" though it is never very cold by my standards...We get a wet and dry season (winter) but it can rain any time.

I probably grow more perennials than annuals, though some you could treat as annuals I suppose.
Vincas and bedding begonias generally hang on for more than one season. Dahlias, Mirabilis, Coreopsis I like too as they are very hardy, gerberas and gazanias. And geraniums.
Because of my soil conditions and the fact that I need to grow a lot of things in pots, I am not too adventurous.
My favourites in annuals would be pansies and violas in the cooler months, torenias, lobelia , nasturtiums and petunias in the warmer ones.
I have tried and failed with foxgloves and many of the hollyhocks, just too hot. though Musk mallows (malva zebrina) love the conditions. So do things like the old fashioned statice, cornflowers, nigellia, queen anne's lace, cleome
I've also found powdery mildew a problem with plants like verbena, snapdragons, stock, calendula, poppies , forget-me-nots and zinnia and kind of given up. Though they will grow.
Sweet peas - well again, they will grow but not thrive.
Coleus love the warmth but can be finicky. Balsam as opposed to impatiens, do well.
Salvia, especially the annual blue, red and white, are good. Portulaca and mesembryanthemum are fine in a sunny spot.
Ornamental chilli are a good filler there are some nice colours of fruit and variegated leaves.
sorry a bit of a ramble
I have a friend in malaysia - nearish to KL but who visits the highland areas too - said she would be happy to contribute - if you would like to PM me through "my page" I will pass on her e-mail address if you would like to chat to her.

Torenia does very well in my Tampa Bay summers..avg high 90-91F lows 75F humid wet, also there are great coleus that thrive, and cut back, will come back the following year. Even reseed. Crossandra I use with great success, too, and cut back late fall come back the following year. I cut these back hard.