There appears to be quite a variance in post-surgical protocols regarding physical therapy.
The big fear post-surgery is a fracture of the femur. Very small chance of that happening, but as that typically results in revision to THR, some doctors (including mine, Dr. Gross) restrict certain activities for the first six months after surgery. While I think many physical therapists would do, and do do (ha-ha) excellent work with HR patients, I think there is concern that a physical therapist who the surgeon doesn't know may not be up to speed on HR and could do something that might jeopardize the head of the femur. I was an out of state patient so Dr. Gross could hardly be expected to know anything about my local physical therapists. Also, regardless of what the PT does or doesn't know, the head of the femur is at-risk for a period after surgery, and many (I imagine most) surgeons recommend great caution concerning it.
So few people get HR in the U.S. (relatively) that I am sure there are even some physical therapists who are not familiar with the distinction between the two surgeries (though I bet most are). With THR there is no post-surgery risk of fracturing the head of the femur as there is no head of the femur.
I started with PT at six weeks and did once a week for two or three months. I really hadn't intended to, but I went to a PT practice for a diagnostic to report back to my surgeon, and they misunderstood, thought I was coming there for PT and I was just too much of a wuss to correct them... I made sure to discuss the surgery and my surgeon's restrictions with all of my therapists (there were three of them - they kept leaving the practice, so i finally gave up and did as well). They were all very capable and I thought PT was very worthwhile, though mainly to keep my nose to the grindstone about walking, light exercises, etc. I had been a real slug until that point.
To echo Hernanu's post, post-surgery protocol is really up to the surgeon. So check with him (or less likely, her) and proceed accordingly.
Mike
P.S. Sorry. Was a little flip. The proximate cause of my stopping PT was the birth of our third kid. Yeah, the PT's kept turning over, but it was really the kid.