"...people think they can drive any speed in Germany...">

Yes we have the idea that there is no speed limits on German autobahns where in fact I think may half of them or so do have speed limits - Germany like in Europe in general is cracking down on speed to a zero tolerance - cameras help that a lot.

Usually the no speed limit areas are away from the larger cities so you're talking about roads with much less traffic. The last time I drove there - about 2 years ago - there were limits near all of the cities.

Sad in a way since I do like the opportunity to drive fast legally (here the limit is 55 mph everywhere) but necessary when the level of traffic increases.

I got a speeding ticket in late july - Hertz billed me the 25 Euros within a week. Have not received the ticket yet. My question is - am I safe to visit Germany again for Thanksgiving? I dont want to face any questioning or legal charges for outstanding tickets when I didnt receive anything in the mail.

Hertz probably billed you just THEIR handling fee for giving your address to the county where the speeding occurred.

Whether the actual ticket will or will not be mailed to you also depends on the amount. As you have not received it yet, it cannot be "outstanding".

And even if it was outstanding, it would not result in legal charges. Late or non payment is not an offense.
In a worst (but unlikely) case scenario, you will be asked to pay the ticket upon entering Germany again.