Hi Alex,
Don’t hesitate to bring 'em both. There is a pretty good tri-community in Singapore with at least 2 or 3 clubs, some really nice races (no cold water !), professional coaching (check out Tribob), and I cannot count the number of olympic size swimming pools (just around my work there are 4 olympic pools). There are also a couple of good tri-specialized shops (TheBikeBoutique, BikeHaus) selling everything gear you need to pimp out.
There is also a couple of good biking groups (check out anzacycling or cycleworx) with daily rides @ 5:30 in the morning and long weekend rides.
Street conditions are OK and it is easy to ride at night (lights everywhere …) the only problem is you have to be really careful about the drivers (sorry if I insult any singaporeans but generally when they get into a car they transform from gentle, nice and courteous to absolute axxxoles …) …
There are a couple of “classic” bike loops for 60 km (Kranji), 90 km (Changhi), and 120 km (both) and if you really want to do long distance you can take a boat over to Malaysia (Desaru) and get in an easy 180 km … OK, for sure you lack in diversity and it is pretty hard to find a respectable hill out here (sometimes I get pretty tired about banging around Kranji for the umpteenth time …but it is better when I am out training with the club and you can set up some brick sessions or time trials. There is also a great park to run in (MacRitchie) with a nice 11 km loop in the jungle and you can extend it easily out to 22 km by heading out to Rifle Range Road.
Tribob organizes some long rides in Malaysia, Bali and Thailand if you are itching for 4 or 5 days of hard riding.
There is even a couple of good mountain bike loops (Bukit Timah) and Malaysia is great for mountain biking (just avoid the cobras and other strange creepy crawlies) … place is mud lovers paradise.
There are a number of really good races; OSIM (OD), Desaru (Long), Langwaki (IM), Bintan (OD), Hanoi (OD), Powerman, Oakley (Duathlon), TAS Biathlon, Busselton (half), … most are really well managed in fantastic hotel resorts. The local bike organization (SACA) organizes some individual and team time trials and every once in a while a crit.
Change out all the screws on your bike to something that doesn’t rust (shimano components are immune but everything bar and stem related seems to choose cheap screws) … and you sweat like crazy (about 3 months to adapt to the humidity and heat … ).
With all the tri-community and number of Cervelos, Planet X, QR, Felts, Scotts, the number of fanatics with Zipp wheels… if you don’t bring your tri bike your gonna regret it.
Anyway, hope my feedback gave you some ideas about the tri-community in Singapore.
Best
pdg