To be honest

To be honest
 

What one is the correct translation to "To be honest"?

To be honest.
Para ser honesto.
Para ser sincero.

I have to be honest:
Tengo que ser honesto.

I would like to be honest.
Me gustaría ser honesto.

I would think the second sentence would be the anwser to my question. However, I thought I'd post here just to be 100% sure.
If the first and the second sentences are correct, when do I use "honesto" in the sentence instead of "sincero"?

Well, the third is probably more likely to be translated as: "I have to be honest".

Thanks.

All your sentences are correct. I don't think of a better way to translate "honest" but "honesto".

A pleasure.

So many ways to the say pretty much the same thing. :)

Gracias por tu ayuda. :)