TO get to Ecruteak, yes, you keep going straight. It's a sort of old-looking town, you'll see the towers first when you get there. To get to Olivine, where we live, you go left until you get to the Moo-Moo Farm, then go down. I'll be sure to not let him know you're coming so you get the jump on him.

When in doubt, you can check your map!