You will have zero problem finding a position in SA. I have heard that the area is short 300 nurses per day - ie if they could hire 300 nurses everyday there still would not be quite enough....We're desperate here.
Non-spanish speaking won't hurt at all. Sure, it'd make things easier if you were, but it's rare to have no one around who is not Spanish speaking. I do recommend taking some courses (offered locally) in "Medical Spanish" just to make life a little easier, but it's by no means a necessity. It's much easier here, even with having more spanish speaking patients.
I'm not an RN, but work in health and am familiar with both in general. Both are well respected.
btw - NW Indiana, or at least not far from there, has a large hispanic population. Head towards Elkhart and you'll find tons of new Mexican immigrants. It's a funny place - near Amish country and you find horse and buggies at Supermercado Rosales

. I lived in South Bend for awhile, and was interested to find significant populations of new immigrants. Then of course there's Chicago.