I've worked Med-Surg/Tele and it is definitely physically demanding!! Most, if not all, of the shift (doesn't matter which one), is spent on your feet, doing basically what NewCCURN said, except with more stable patients.
I, for one, am a H-U-G-E advocate of getting in (at least) a year of Med/Surg before moving on to critical care. The old saws of learning what is "normal" and "getting your feet wet" make a lot of sense. Also, as a new grad you will have more than just assessments and procedures to learn. There are also time management, prioritizing, and critical thinking skills. It would seem those would be easier to get a grip on in a less intense atmosphere. Besides, if you take one position, you can always move into the other at a later date.
If you are unable to do much standing, walking, lifting, etc, you may want to investigate positions in an environment where patients are more stable, like Rehab or Long Term Care, or even an office setting.
Best of luck!