Even though its probably NOT the reason you came to Zurich, if you want to head to a bar/pub with fun atmospheres, good drinks and pub food and where people speak English then here are a few suggestions:
Paddy Reilly's (everyone calls it Dubs, short for Dubliner's, still though): http://www.paddys.ch/zuerich/
Probably the best one and my favorite watering hole.
Oliver Twist: http://www.pickwick.ch/zuerich/
Great place aswell, bit smaller, amazing Aussie style burgers!
The Lion: http://zuri.net/adr/24208/the_lion.htm
Slightly more upscale, winebar/pub. Still awesome spot, right off the Bahnhofstrasse.
Big Ben: http://www.bigbenpubzurich.ch/
Great little English pub right on one of the most happening streets in Zurich.