While I will recommend the HF Clinic, I'm not so sure about every 3 or 4 months.
Last time I called HF, the guy got a little pissy with me on the phone once he determined I was not engaging in Bare Back Anal with men. In a nutshell, I was told that if I had been tested within the last 2 years to wait for my 2 year anniversary. Also, you have to wait 3 months since your last Bare back session - which is again bullshit.
HF is set up to treat HIGH RISK people - gay men, IV Drug Users who share needles, Sex workers.
They didn't have too much time for me. Truth be told, my impression was that the guys manning the desk are a little more (nay a lot more) militant Gay Boy than the doctors in the back. They think of the HF as "should be gay only" but since they'd lose their funding if they operated like that, they have to tolerate the straight / slightly kinky community. In a way, I actually understand that, because they undoubtedly get piles of little straight boys and girls who are "over tested" - every time they fuck someone different (which is ABSURD) and they (the little straight boys and girls who are looking for a free BB sex card) are burdening the system - a system which should be there to service those MOST at risk.
So, I just called them up a few weeks later and gave them the wrong (or is that right) answers in order to get an appointment.
My personal opinion would be once a year if you're a straight male and who cares when your last Bare Back sex was. (They figure that you should use condoms for the 3 month period, that way you will know you are clean. I figure, well, I understand that, but there is nothing to say that I had not contracted something prior to that and better to know.)
HIV testing at HF is annonymous, but you need an appointment. They will give you the pop quiz on the phone to see if they even want to see you. They can give the results right on the spot - though they will give you the safer sex lecture. (Mind you, that few minutes you wait for the bubbles in the test kit to form are definitely a time for reflection.)
STD testing is on a Walkin basis, but you need your health card and it takes about a week to get the results.
I'd like to say that it is "Hassle Free" but it's really not. There is hassle. Hours are extremely limited. The one good thing about it though is that you're just another horndog as far as they are concerned and they don't really care what you do in the bedroom.