Hi SDG - Obviously, this is a hard decision that only you can make. I struggled with the same issue.
I did my practicum at a rehab hospital. I found that the types of health problems that the patients faced at the rehab hospital were more acute than I'd expected since many of the people were elderly (and had peg tubes, foleys, etc. a few IVs). Though many were also young (accident victims, etc). There was more "med/surg" type nursing than I imagined there would be (though it was not a med/surg unit).
Having just graduated, many people in our class went straight into the NICU or mother/baby (or another specialty). (Not all hospitals require a year of med/surg first). Some people though did choose to do a year of med/surg. During your nursing school years, you'll have the opportunity to experience different areas of nursing (Some folks wanted to do pediatrics, until they were a student nurse on a pediatrics unit. Some folks wanted to do NICU, until they found that they enjoyed the Adult med surg floor better.
That's interesting that the hospital has a program for you to sign up with them before you have started nursing school (and have had a chance to experience different areas of nursing). Some hospitals have internships for people between their first and second year of nursing school. Our school had a program in which seniors could choose to do their practicum at a hospital in a particular area of nursing, and then stay at the hospital for a year (the hospital paid their last year of nursing school)
During my practicum at the rehab hospital, I met patients with strokes, amputees, accident victims, spinal cord injury patients, brain injury patients, etc. I don't feel that being in rehab hinders an individual from being able to deal with more acute cases (I know this was your primary concern). In fact, I have a lot of respect for rehab nurses......especially for their assessment skills and working with the newly handicapped. (I also learned about interesting disorders like Guillain Barre and Charcot-Marie-Tooth Syndrome). They seemed to deal more with the patient .......not as much with the machines. It was very holistic. After passing the NCLEX, I plan to start working there in the fall (after a long debate with myself med/surg or rehab, med/surg or rehab. I found I really enjoyed the education aspect of rehab, and working with people who were at a critical point in their lives (losing a limb, the ability to speak, etc.). And the "nurse manager" at the job I will be reporting to in the fall, did several years of rehab...and then she switched for a few years to med surg..... She felt her rehab skills actually benefitted her when she later switched to med surg.
It's a hard decision that obviously only you can make. I wish you well.