I think that users should be wary of asking a question like "How can I say XXXXX?" and just leaving it at that. However, just a little context can make such a question entirely allowable.
How do I say "I like pizza"?
How do I say "I like pizza"? I need to introduce myself tomorrow to a Korean speaking client at work and I want to use a bit of Korean. I know next to nothing about Korean though.
The second question is pretty much asking the same exact question as the first, but the added context of the second helps us answer the question better. We know what politeness level to use and we are aware of the asker's abilities in Korean.
This being said, I think that we should be rather loose on this. I would personally prefer that a user ask a weaker question than never ask any questions for fear of being rejected.
So, conclusion, I think that we should be willing to allow questions like "How can I say XXXXX?" while also pushing for the askers to provide context. As long as the request for translation is less than a few sentences, I am fine helping.