How do I switch to Telus US/Canada plan without having to take unlimited data?

You'd probably be better off asking Telus that instead of koodo...

And in general for these sort of questions, the plans you see on their website are what you can expect to get. If you're not able to select such a plan online, then the answer would highly likely be no. Special promo plans aside of course.

No way to get a better price with less data as their CAN/US plans all come with unlimited data but they do have employer discounts if you work for select employers and they may have something available if you’re switching from Koodo.
It would be something to ask Telus about though like the others said.

Are you a frequent traveller? If not, you are better off getting a U.S. prepaid plan while roaming, so you do not have to limit yourself to a few plans with those features. 

Turn the tables and look the other way. AT&T US/Canada/Mexico prepaid may be worth your while depending on how much time you spend in the US.