Personal training and physical therapy a quite different. Even outpatient orthopedics is quite different (I work in outpatient). I would suggest shadowing several different settings. Acute care, inpatient rehab, and maybe some pediatrics. I feel I would have been happy working in almost any setting, even the dreaded SNF but I am pretty flexible and have a wide array of interests. There are a variety of options out there. I personally love my profession, I have had several potential "careers" and I find the downsides to PT much more manageable.
Downsides to physical therapy include those that are happening health care in general. Things like decreasing reimbursement, high patient volume, and job saturation in some areas. Working with insurance is always a challenge and sometimes it feels like I am talking to a my stubborn three year old son about eating his vegetables.
I will say job saturation really isn't much of an issue if you are open to working in different setting but if you are set on outpatient ortho or inpatient care you might struggle to find a job that treats you well in many places. However, if you are wiling to relocate for a few years you won't have issues.
The biggest issue however is cost of education. Other professions are having this issue but many of them do have significantly higher base salaries than we do as physical therapists. I do support the APTA and other associated professional organizations but this is the single biggest threat to our profession and they don't seem to want to talk about it, at least not to the extent they should be. It simply doesn't make sense to be a physical therapist for most people, if you can keep you debt under or around 70k you can make it work but even then it might not make sense. Suggestions to keep your debt down is avoid private schools, go to your state school and if you don't get in don't go to PT school. I had a wife who worked full time, made money sporadically, had some small scholarships so I ended borrowing about 54k but was unable about 6k in interests bringing my debt to approximately 60k and I still hate it and it significantly alters my financial situation.
I am a firm believer that you don't need to sacrifice everything to "chase your dream". You could probably be successful and enjoy your career in many different fields. What is more important is that you can work with the right people in the right environment. I love my job but I could be just as happy working construction, commercial fishing, teaching, etc.