Before declining to offer an opinion, it's worth considering whether you'd benefit from the decision being made. (For instance, you could get a prompt dinner.) If so, why not offer a little help? Decision making can be tiring work, and any input can make it easier.
You could:
mention any limiting factors (i.e. I have $20 or 1 hour)
Mention options that are convenient
Offer support to the person who makes the decision (particularly if you can avoid critiquing their choice).
Before declining to offer an opinion, it's worth considering whether you'd benefit from the decision being made. (For instance, you could get a prompt dinner.) If so, why not offer a little help? Decision making can be tiring work, and any input can make it easier.
You could: