Matthew 10:16 (ESV)
16 “Behold, I am sending you out as sheep in the midst of wolves, so be wise as serpents and innocent as doves.
It is hard to judge the intent of the person's heart. Could be they are more interested in freindship, or it could be they just are trying to get you saved. If it is the opposite sex, it could be they are interested to find out if you are a Christian. That would be wise before asking someone out. Too shy to ask directly, but hopeful.
I was taught friendship evangelism and use that model all the time. I do not set out to do it in a disingenous way. I truly care about any person I attempt to friend and at some point hope to share, invite them to church etc. I will say that I think that everyone should evangelize at times to reach a large number of people. But there are some instance too where the quality of the relationship is important.
To me getting the card or tract is meaningful and caring. Even if that person was simply being nice to share the gospel, where is the harm? Be more worried about those wanting money, sex, adoration or other selfish reasons for initiating a relationship.