If you're around campus/downtown, you could stay fairly busy. You will be competing with a lot of other Uber drivers for those pings. Boise is over-saturated. Maybe 2 pings an hour. Keep in mind these will be short trips usually. You can get paid as little as 2.50 per trip for a minimum fare. Don't count on any tips, especially on campus.
Looking at the Sat/Fri projection again, working a 6 hour night probably only net you $100 a night at best.
In summary, Boise is a over saturated, low demand market. You can only expect to be busy Fri/Sat nights, the rest is hit and miss. Lot's of low pay short trips, no tips to speak of. (that being said I did get a $30 tip from 5 drunk bacherlettes one night-you never know-some nights people are generous, avg is about 1 in 10 though)
Here are real numbersTo earn $1200 a month I would have to have to work approximately 85 hours a month. I am at 20% to Uber. As a new driver you would be paying Uber 25%, so you're number is roughly 10% more, 90 plus hours. This is based on my log from last month. That's before expenses btw. Also that assumes in that 90 hours you would be busy 100% of the time. Your mileage return would be roughly .70 per mile.
If you want to work just Friday and Saturday nights, you can ideally make $300, working 9 to 3 AM.
The $300 is for BOTH night combined, and I over estimated. To make $150 a night you are looking at a ten hour shift.