Would using Zapier to collect Gravity Form submission and pass them to Marketo count?
If you're trying to filter on this data upon lead creation, it will be hit or miss. The inferred data is populated asynchronously, so there's no guarantee that it will be available upon creation. You'll want to setup a wait step and check about 5 minutes after creation instead of at creation.
Are you suggesting setting up that wait step in our lead is created smart campaign? Or in our Sync to SFDC smart campaign?
This usually just affects lead is created campaigns, but it depends on which campaigns are checking the values, so I can't really answer that in the abstract.