unbelieving
dubious
doubtful
skeptical
untrusting
cautious
apprehensive
hesitating

Be dubious for your own safety.
We live in a society of doubt, where from young ages, children are taught about the harms of trusting someone:
- “Don’t talk to strangers”
- “Don’t take candy from strangers”
- “Don’t get in a car with someone you don’t know”
- “Don’t open the door for anyone”
- And the list can go on forever…
However, I agree that trusting anyone is a risk.