Just a crazy thought...can a traveller just show up and expect to find a place to stay? I'm thinking of travelling to AC from Aug 21-27, and I wonder if this is possible. For instance, in many of the Greek Islands, the small hotels, pensions, etc. actually meet all of the planes and ferries to try and entice you to stay with them. Often you get better deals this way. Anything similar on AC?

Should not have any problem finding a place to rest your head at all at that time. Never experienced the meet & greet at all, however. That said, the taxi drivers likely will make a recommendation or two!

this time of year you will be fine. However, why don't you book a room for the first night? I only say this cause if you arrive on a later flight and have to look around until you find a vacancy, the hotels here are mostly not 24 hours, most close the front at 5 or 6pm.
If you are on a budget and want to be in the middle of town, try Spindrifts or Lilies.

yep. i often recommend what krazyK says above

we stayed at coral beach and they were very nice there. They have a website if you google search them.

We also stayed a night atthe Holiday and liked it as well, but it cost a bit more.