Learning Model Theory

I really like Introduction to Model Theory by David Marker. It starts from scratch and has a lot of algebraic examples.

For a free alternative, Peter L. Clark has posted his notes Introduction to Model Theory on his website. He says no prior knowledge of logic is assumed and the applications are primarily in the areas of Algebra, Algebraic Geometry and Number Theory.

You could give Bruno Poizat's A Course in Model Theory a try.

If you are feeling particularly ambitious, perhaps Model Theory and Algebraic Geometry (E. Bouscaren, ed.), which intends to gives an introduction to certain concepts in the interplay of model theory and algebraic geometry, with a view to an exposition of Hrushovski's proof of the geometric Mordell-Lang Conjecture. If nothing else, this work should give an idea of what concepts of model theory have found application in algebraic geometry (at least in the aforementioned proof), which should give you an idea of perhaps what topics to look for in a model theory text.