GeoKit / Form Validation

I am new to rails and have been scouring the web for the past two days trying to figure out 2 things.

1) I am currently using a form with 2 models. The first is person, the second is address. I attempted to duplicate the two models on one form as seen in Advanced Rails Recipes and Railscasts, and they work fine - except when there are validation issues on the address piece it just returns saying "Addresses is invalid". I would much rather it say "Street Address is blank" or "City cannot be blank" any ideas on how to do this?

2) In using the GeoKit plugin I am attempting to use the acts_as_mappable piece so when I create an address it adds the lat and lng to the DB. If I choose just 1 field and specify it this works fine and the table populates, but I want to concat all of the form values (Street_Address_1, City, State, Postal_Code, Country) and pass these in as the location. It appears GeoKit expects address to be a single field - which will not work for my application. I am not opposed to using another plugin, it just seems GeoKit is overall the easiest.

Any help would be greatly apperciated, and please go easy on me, I am attempting to learn RoR on and old AWDWR book, and Advanced Rails Recipies.

I'm thinking that perhaps the answer to my second issue with GeoKit is simply needing to concatenate the fields for my address form into a string, however, no matter what I try I get errors. Any suggestions on how to do this?