The Marketo landing pages are not responsive because of their use of absolute positioning.
I've had good experience with creating responsive landing pages and dropping in an iframed Marketo page with just a form. I recommend starting with a bootstrap template that is designed to be responsive and building from there. Here are some great ones - http://www.designrazzi.com/2013/landing-page-templates/
You can even add a css viewport to your Marketo landing page, but usually a one column form will fit nicely on any screen size.
If you have your heart set on a truly responsive Marketo page, here is an article from Yesler on how they did it - http://edwardunthank.com/blog/how-we-made-a-responsive-marketo-landing-page/
...Sorry can't help you with the latte!
Thanks Josh and Alok! We'll be looking at all of these links and sorting out the best route. Appreciate the quick response and will follow-up with add'l questions as we dive in a bit more. - J