SpamAssassin on a work station?
 

Can I?
Should I?
How do I?

Is it possible to have my mail come from my pop account, and filter through SpamAssassin and then into say evolution?

I just set this up last week. Not only is it possible, it rules..
Here is how to set it up. Super easy and only takes a few minutes.

http://krath.dk/linux/evolution_spamfilter/

installed it, ran tests as seen in another site. however, when I type spamassassin -P I get no response and I don't get a second prompt

So you have spamassassin setup correctly (local.cf configed)
and evolution set up to route mail through it?
Are there entries in /var/log/maillog mensioning Spamd?
I am not sure you can call spamassassin from a prompt that way. Anyhow check your maillog and that should give you a clue where the break in the chain is occurring...