Yes...I see one problem with an open hose. The lint and dust it would blow out into the garage.
There are a few options there for just rescuing the heat in the winter. I have seen a filter cover that goes on the hose and I have seen people put old pantyhose on them as a filter. That seems to work as long as you empty it often.
Now if you mean actually heating the whole garage with it, I doubt it would be very energy efficient or do a very good job. The dryer wouldn't last as long either running it all the time. Just my opinion.