I flew this route at the end of July. I am a 1P, and I had some questions about this. So I tested it, and asked a lot of questions.

As for making reservations on the phone, this is considered an international flight: "Is your itinerary solely within the 50 United States?" NO.

As far as boarding time is concerned, it is an international flight: 1P rez agent told me they recommend arriving 2 hours prior to the flight.

RCC: I went in, ready to do battle, and the lady I spoke with said that some of the RCC agents will allow SJU pax into the RCC, but some won't. This particular agent said that if you're forced to arrive 2 hours prior - just like other "international" flights, then you should have the benefit of the club. I, along with 2 other pax I was travelling with got in.

Also, interestingly, RCC agents only announce international flights, and the SJU flight is one that they announce on a daily basis.

I hope this helps.