Economy picking doesn't necessarily mean down up down down up, etc. The term means using the most efficient (least motion) picking pattern for a given passage. The upside to this is that you can achieve faster speeds than with alternate picking. The downside is that it's hard to improvise with economy picking because you usually have to stop for a second and think out how to best pick a passage with economy picking.

Take this passages for example (paste in notepad)

e |---9-10-7-9----7----
B |-7----------10---9--

Alternate picking, there's no thought - down up down up down up down up.

Economy picking is harder to think out, but faster once you get it - down down up down up up down up

I suggest sticking to alternate picking... I mean you can get absolutely monstrous speed with alternate picking... hell, some of the players on this board are speed demons without using any economy picking (not me though, I like to stay under 140 staccato :)