Good idea! I though about possibility to get to create survey page, and block "create survey" button while you are not signed in, but then we still will not see further process :/
How about no-registration test accounts (test123, test1234, etc.) that are limited to 1 survey, 3-5 questions, for polling 1-3 people, and that expire in 3-7 days? This should be enough for people to see if they like it.
But if everybody will have access to the accounts there will be mess. Unless you mean something like a button that will generate a sample account for you (and that's actually not a bad idea)