road vs tri bike--training in developing country

I know I'm opening up an old can of worms, but..... I'm about to go to Singapore to "adopt" a bike, and would appreciate some insights into road vs. tri for my unusual situation training in Vietnam:

1. In training, the bike will get ridden on the road once a week for 9-10 months of the year. On this day, an industrial park is closed to vehicle traffic and it is safe to attain reasonable speeds on a bike. (It's possible I might mount the bike on a trainer if I can find one locally, though I already have a stationary setup.)

2. Access to above park is on a parkway with very chaotic traffic. Not too bad heading over at first light, BAD heading back a few hours later. It is critical that I be able to see, easily steer, brake, stop on a dime, get off the bike when needed at lights. I do have a very protected area where I can practice bike skills before heading to the parkway, but it's only a few hundred meters long--useless for training.

3. Bike will be used mainly for training and triathlons, mostly flat to rolling, in Asia, and possibly Hawaii or California in the summer. Would also like to use it for some pleasure riding in the Pacific Northwest in the summer (hilly; live on top of a very steep one).

4. I usually train here in a small group of 2-5 people; in the States (1-2 months a year) often ride solo for training or pleasure, both roads and bike paths--one has some road crossings, the other doesn't. 

5. I haven't ridden a road bike in 20 years. I am confident and pretty fast on a mtn. bike. I am a strong swimmer and runner for my age group and would at least like to be fast enough on the bike to be competitive in my age group.

6. Races would be mainly sprints and OD, possibly a half-ironman. I don't forsee trying to train for an Ironman in the next decade or so!

7. I have a modest income and not much financial or job security--contract to contract. Going out and dropping several thousand on another bike in the near future is not an option.

Any thoughts on the best set-up for this? I'm leaning toward a road bike, with the option to add aerobars for competition if I get feeling confident, but my biking friends aren't triathletes so thought I should let some triathletes weigh in on this. Any specific models to recommend, or does this depend mostly on fit?

Thanks in advance!