Hi Jeanette,
When I set this up, I first figured out what time in my timezone (EST) the email would need to be sent at in order for it to be delivered to that timezone/region between 7am-9am their time. Once you have that figured out, you can use a series of send email and wait steps in your batch campaign to "throttle" the email send based on their geographic location.
Here's an example of one we set up. We tag our leads as they come into "Email Flights" based on the Country field:
There is also an Idea on the community to have this be a feature in Marketo that you can vote on:
Send emails based on local times