If you're downtown there are lots of places to eat and have fun. Just walk, no need to drive down there unless you're going out to games. Toronto is generally a safe city, but keep in mind it IS a big city and we have our share of crazies down there. The club district is Richmond St West between Bay and Spadina, Queen St West between University and Bathurst has a lot of shops and food options, King St West of Spadina is an older crowd club area, King and John is the theatre/symphony area and they had restaurants there that cater to that crowd. The Eaton Centre on Yonge St between Dundas and Queen is the big mall down there and has a food court and some restaurants. Bay St is the financial area so you get more offices up and down there. On the waterfront you have Queens Quay which is touristy and has some nice scenic waterfront. The Aquarium is down by the CN Tower and the Rogers Centre. If you're rich you can catch a Leafs game, they're rink is right down near the waterfront at the foot of Yonge St. Scalpers tix will cost you $100 minimum, up to $500 or $600. I think the Raptors start up in a few weeks as well. Those tix are cheaper than Leaf tix and they play in the same building. If you're rich, try the Harbour 60 steak house at Yonge and Lakeshore..it's awesome but will set you back probably $100 per person. If you want some specific info on restaurants it really depends on where you're staying exactly.
As far as traffic, there are 3 main highways into and out of the downtown, Don Valley on the east (north south), 427 on the west (north south) and the Gardiner (east west along the lake). Depending on time of day, as others have said, they're a parking lot. We have a typical, brutal rush hour. Lakeshore Blvd is an alternate at times but it really depends. Sometimes surface streets are a better bet but it really depends on where you're trying to get to. The 401 goes across the city parallel to the lake but 10 miles north of it. It's also a parking lot in rush hour. Try to avoid driving on weekdays between 7:30 and 9:30 and 4 and 6.