I've had both good and bad relationships with them.
Some simply don't know very much about autism--they believe it's a kids' disorder, or that it's always severe, or that if you can talk you don't have it. That's a problem; more so if they're not willing to learn. A few THINK they know a lot about autism, but actually just have stereotypes in their heads that they apply to everyone. This is not helpful.
Others have a pet disorder that they like to diagnose everybody with. I met one of these when I was first getting into the mental health system; she diagnosed me with borderline personality disorder, a diagnosis that has made several counselors since then laugh out loud at the absurdity of it (I have many of the exact opposite problems that people with BPD have!).
But a few will take the time to either learn about autism, or already know a good deal about it and , and will work with you to find solutions for your everyday problems. The psychologists I've met have had about a 50% chance of being in this category; but I am told that I am quite good at communicating in a formal manner, and that many psychologists understand me well because I communicate in a way that is quite similar to a psychology professor! (For example, I may come in worried that I'm developing another episode of depression and report "anhedonia and sleep disturbances".) Other psychologists have apparently been intimidated by this, though; but the ones that have been most helpful and given the most useful advice were generally willing to accept that I had researched autism and that the more I knew about it, the more I was able to solve my autism-related problems. Some of them have even dropped the simplistic language they use for many patients and will use the more specific language of psychology to explain what they mean, and this has really helped because we both know exactly what they are referring to.
So--really, it is probably a matter of luck. Do you need help before August? If so, you should probably try it, if only to find some way to survive until then. If not, waiting isn't the end of the world. But do make sure that this autism clinic has some way to evaluate adults, especially "high-functioning" adults (i.e., verbal and living independently), rather than only children.