Quick question for all you Flyertalkers.....I'm planning a trip to Madrid for a 10 day stay. The best fare i have found for the dates i am looking at (mid-april) is $586. I have miles on both American and United....would it be better to burn the miles or pay the fare and earn miles...and save the miles for later.

I guess the question is what for this time of year and the European market...what would be the better choice...miles or $$.

If you are thinking about using miles better check to see if there are any award seats still available on the dates you want to go. US to Europe routes are sometimes very hard to get award seats on, especially since you are only looking ~8 weeks in advance!
United does not have any service to MAD from LAX (nor to MAD from anywhere else in the USA). The best connection would be on US via PHL.You would have to get a Star Alliance award using UA miles for that ticket. The other option maybe LAX-FRA-MAD on LH also using UA miles.
I am not that familiar with AA and OneWorld, but I do know that Iberia has no service to LAX but offers a code share with BA via LHR.

If I were you, I would rather buy the ticket with $$ and earn miles and I would also use miles to upgrade myself. LAX-Europe is quite a long flight. Of course if you have enough miles book an award ticket in C!