If your offer is clear enough, you should.
On Roast & Promote, people join to get feedback, sometimes to also give. Because that's what the group is about, to get and give feedback on your content, websites, community and ads. And they usually do it right away, as I got 71% of members above level 1 (going up to 76% sometimes).
A lot of times when communities have an engagement problem it's because there is no clarity on how we should engage or because it seems too complicated to do so.