I guess to me it's a matter of "do you want to". If you want to no hill is going to be too much. There is even a Pedicab company in Denver.
About pedicabs, rickshaws, pedal cabs, and bike taxis in Denver Colorado
I love this calculator. Again, there really is no limit to what we can do on a bike given unlimited time & equipment. I think we're just trained in the US to think that it's going to be "hard" to ride a bike (take the bus, walk) and that paying for a non renewable fossil fuel powered vehicle is "easy".
How Much Weight Can A Bike and Trailer or Cargo Trike Carry?
OK rant over. It's taking away from the point, awesome vehicle choices
Chole