I've had a similar experience as mscaffrey - most of the students I've met here at Cambridge seem to love going out drinking and clubbing, and there are several big 'student' nights per week. It may be a small-ish town, but it is hopping with students and a lot of the social 'scene' is geared towards them.
Cam also has many other ways of socialising - swaps with other colleges, bops, drinks with sports teams, and dinners in your college that are often served with a gallon of alcohol (more or less). It's not just clubbing here, but you will find plenty of people who enjoy going out, drinking etc. in many forms, so I wouldn't be scared of everyone being very nerdy or work-oriented.
Yes, the workload is quite high and there will be essays (though how many depends on which subject you've chosen), but the terms are short so it's concentrated into an intense period, but then you'll have weeks free afterwards: 8-week terms here versus 10 or 12-week semesters elsewhere. Again, depending on which subject you've chosen, the amount of effort needed per week will also vary.
Do bear in mind too that at all universities there will be certain 'crunch' periods when everyone is working and the social life drops off a bit - usually it's towards the end of term as deadlines etc. loom, and of course during exams. That is unavoidable anywhere you go really.