Waterloo is quite a bit smaller than Leeds, maybe half the size if you include Kitchener. That being said, expect the things-to-do-on-weekends to be sized down proportionally. Wilfred Laurier University is just down the street, so bars and clubs are definitely vibrant, then again you're usually going to have to go to Toronto for big name concerts.

I recommend applying for Mackenzie King Village. It's a suite style where you get a private room but share a living room and kitchen with 3 other upper year students (They won't plop in with 1st years). It's more expensive than other places, but has AC and is close to the math buildings.

There are a lot of asians in the math program at Waterloo. You'll hear mandarin or cantonese conversations on every floor. On campus, you'll see a mix of every nationality. Many students come from abroad or are children of immigrant families, so there's an inherent study hard, play soft dynamic which kind of defines the school.

No violence or crime. People are very friendly, but not the kissing-on-both-cheeks friendly. We generally ignore strangers on the bus but we'll be pleased to show you which way to go if you're lost. UWaterloo is biased towards males. Ratio is about the same as in blackjack. I'm sure that ratio is cancelled out by Laurier. When in doubt, pull out your best Hugh Grant impersonation and you should do much better than local residences on all fronts.

tl;dr: Nightlife worse than leeds. Go MKV. Asians. British accent will get you laid.