I use a laptop for estimates and drawings. I don't have a portable printer. I print at the office, or just show the screen.
The drawings are put on a CD or disc if they fit, and plotted at Kinkos. (Full size prints), or I do 8 1/2 X 11 or 17 x 11 in the office, if I can get the detail on a small sheet.
I had thoughts about getting another laptop for the service trucks, but can't justify the costs at the moment. Most of our service work is for national chains, and property management co's, and the billing goes thru our office.