I'd get a seperate router/access point that is highly directional and point it at the garage. At that distance, even through walls something like this would probably work just fine
http://www.amazon.com/dp/B003CFATOM/?tag=snbforums-20 One, or two of those on an N150 or N300 router plugged in to your home network should extend your wireless in to the garage just fine. At that distance, unless it is a really big garage, the wifi coverage should beam over the entire building.
Or you can grab a couple of inexpensive Engenious P2P outdoor bridges and then a seperate router inside of the garage. A pair of these
http://www.amazon.com/dp/B004SBG48E/?tag=snbforums-20 one outside your house and one outside of the garage pointed at each other on a channel seperate from your home network and probably set to 20MHz (unless you don't use 2.4GHz in your home much at all) would work really well. Then a halfway decent N150 router in the garage itself, also on a different channel and you are done. Probably all done for under $160.
The later would your best bet, in terms of wireless/link speed.
I currently have a shed located about 80ft from the antennas on my garage and I get about -70dB of signal inside of the shed with the doors closed, with 5dB omni's just outside of my garage.
So with a 14dB, directional antenna, figure inside your garage, even taking in to account slightly further distance, you'd probably get -60 to -70dB, which is fine for a decent link. Its not going to be mind croggingly fast, but it should support web browsing, email, at least one "HD" Netflix stream, etc. Probably get at least a usable 10+Mbps and probably higher.
I'd personally consider the cheaper route with just the outdoor directional antenna hooked up to a new indoor router in your house (antenna mounted outside of course) (or a couple of antennas if you really want). Then you can easily reuse the AP in the garage once you run the wires.
With the outdoor APs, you probably wouldn't ever have a use for them once you run the network wiring.
Or, as suggested, home plugs. Just google home plug networking, or check out the home plug networking sub-section on the forum here.
They are inexpensive and tend to work okay, just not great speeds.