Dereck47 answered your specific question correctly. If your chosen SSD is fast enough to exceed the data rate of SATA 2.0, and very few are, it will be restricted in top speed. But frankly you won't notice it except in benchmarks. A SATA 3.0 SSD will run fine on a SATA 2.0 mobo.
To add, your case and OS may be more the "issue".
If your case does not have a 2.5" cage, you will want an adapter to fit the SSD into a regular HD cage.
If you're running Windows7, the "trim" command is implemented that keeps your SSD running (close to) as new. In other OSes you may have to do some periodic manual maintenance.
Since SSD storage has limited life (vs HD platters), SSD controllers implement many techniques to optimize writing data. These techniques can/will lead to significant degradation of performance if the SSD is not "cleaned up". A full and totally accurate explanation is quite long, hence the wiki refernece.
The article on SSD is refreshed often and allows you to choose based on budget, desired performance, capacity requirements, etc. Its a must read if you are new to the market, or buying an SSD any time.