Will definitely fit the wheel. I assume it will fit the car just fine, but there are better places to answer that question than here.

Two things to consider: width and diameter.

The width of a 205 shouldn't be a problem, I wouldn't even think about it.

The diameter of the tire is what's going to affect things like overall gear ratio and speedometer error if you get it wrong. The gearing effect can work in your favor (smaller diameter) or against you (larger diameter). Either way you want to be fairly close to stock diameter to keep the speedo reasonably accurate.

There are lots of tire size calculators out there that can help you determine what will fit and what won't. Here's one:
http://www.miata.net/garage/tirecalc.html