Don't feel like you need to limit your search to urban centers for lots of sick medical patients. Most tertiary care centers will offer you this type of population. Lord knows, we see tons of very sick patients. Central lines, tubes and pressors are very common and we're not exactly in a dense urban area.
You want to be were there sick people go. They go to tertiary care facilities. Look for those and you'll find the sick patients.
As for the ICU admit rate, I've worked in several places now and see what a huge difference floor capabilities make. In one place, I have to put anyone with a DBP > 100 in the ICU!
At S&W, unless you're on a vent, you're gonna have a hard time getting into the unit. I used to think pressors were an automatic unit admission. Not so much anymore. I've sent my last couple of CHFers on BiPAP and NTG drips to the floor.
FWIW, our numbers are around 23% admits and 7% unit admissions (of total admits; ~1-2% of total visits).
Take care,
Jeff