will the standard jr servos work on the ultra stick 60? or should I go with the 537?

Standard Servos work ok on the US60 but the 537 would be a better choice if you can go to them.

It really depends on how you plan to use it. If you just sport fly, standard servos are just fine. If you are going to get aggressive and want 45 degrees of throw - why not, it is fun - then buy the best servos you can afford. You can always use them later on the next airplane.