Okay, so we might not rent the car that would cost us $117 for 5 days and instead get a few alternate transportation modes.
To get from the airport in Porto Alegre to Gramado we will take an inter-city bus from the company citral.
I've been watching www.booking.com to get a decent hotel downtown or within walking distance to minimize our need of long distance transportation
Then to get to the places that are further away, hop-on hop-off bus with brocker turismo:
This page has a link to the map of all the stops. One day ticket costs R$49.00
And to go back to the airport, since it is an early flight, we will have to schedule a shuttle. There are a number of companies that do that:
brocker, vmc, liga, jusepe ...
here are some links: