The Society is working hard to emphasize the "balanced" part of that statement, which means missions to varied targets, as well as research funding for scientists and technology development that will ensure access to inhospitable planetary environments in the future.
In this statement, we mention something called the Decadal Survey a lot. The Survey, or "the Decadal" for those not up to date on the latest planetary science community lingo, represents the official consensus of the scientific community about mission priorities for the decade spanning 2012 - 2022. Now when I say "official consensus," I don't mean that every single scientist agrees with the report, not by a long shot. But it does provide a pretty decent representation of the planetary science community's priorities as a whole, and is the end result of a long process with deep community involvement. You can read the whole 410 pages here, or (like many people) choose the more concise executive summary. It was created to help guide Congress, the Administration, and NASA when they make decisions regarding funding and mission selection. It's not holy writ, but it is important and helps prevent a fractured, divisive battle for funding within the scientific community.
The Planetary Society, like the scientific organizations listed earlier, supports the priorities of the Decadal Survey. The first priority is a flagship (i.e. expensive) mission to Mars to collect samples for eventual return. A mission to Europa is a close second flagship mission recommendation. Maintaining funding for small missions, (a.k.a. Discovery-class missions), is considered as important as any flagship. So is maintaining research funding for scientists and funding technology development. This is a long-winded way of saying that the Decadal emphasizes a balanced program, and so do we.
The problem is, of course, that it's difficult to support a balanced program when funding gets cut by 21%. That's why we've been running our Save Our Science campaign for the past year, and are working hard to ensure that NASA has the resources to enable this unprecedented – and surprisingly affordable – program of exploration in our solar system.