It depends on who you're with in terms of cell phone provider. If you're using Bell or Telus, unfortunately unless you have the new 3G phones, you're SOL. If you're using one of their 3G phones, you MAY have service there (3G is still too new for anyone I know to test it). If you're using Rogers or Fido (GSM), you should be able to hook up into their network. But what I would suggest is this... If you can borrow an unlocked GSM cell phone and charger from someone you know here, bring it with you. Then go to the nearest Singtel store and buy a sim card from there. I think it's $35 or something like that and will give you a local number. Pass the number along to the people who need to know it and use that. Topping the card up is not hard to do (and I'm sure your lady can help). Also the rates for calling Canada are much better than if you take a Canadian phone with you and call home. What I do with my friends is tell them my Singapore number (065-9xxx-yyyy) and tell them to text me if they need something...
When you leave, you can discard the card and it will expire eventually.
As for money, $100 a day is cool. Except for a few days where you go for the more expensive stuff (like Sentosa's attractions), I don't see you spending that much money.
Enjoy yourself. Singapore's a safe country. And you won't have to worry about the agency either.