See http://wiki.vuze.com/w/Speed_Limit_Scheduler#Network_Limits

You can set calendar based or sliding limits that will stop xfer when reached (no alert at the moment though). With a multiplier you can select other intervals too

Is there a upper a weekly/monthly limit alert setting?

It would be great to have ability to set monthly transfer limits for users with data caps and have Vuze alert when reaching that user define limit, presented with option to Pause or Stop all transfers until the next Month or a selected date.
Of course when the monthly transfer limit is set, the uploads/downloads will automatically adjust to keep the share ratio balanced and in good standing, so users using this feature don't download more than share.
Maybe there is a way to do this already in a more simplified fashion that I haven't figured out.

Actually

Tools->Speed Limits->View Current...

opens a window with today/this week/this month stats at the bottom

What kind of periods are you thinking of? Vuze currently tracks 'total' and 'session' (i.e. since Vuze has been started) data totals.

It would be fairly straight forward to add a view with

last hour
last day
last week
last month
last year
total

for example