Is a player allowed to announce his intentions for their next turn?
A lot of this will depend on your group and how you chose to look at the rules. Other than giving information about what is in another players hand there is nothing mentioned about players talking to each other. There is a note in an English translation of the rules that I found that does somewhat address this.


  Hanabi based on communication - and non-communication - between the Players. If one interprets the rules strictly then players may not, except for the announcements of the current player, talk to each other. Ultimately, each group should decide by its own measure
  what communication is permitted communication. Play so that you have fun! 


I will note some things that my friends do when we play this game all of which are done without the active player asking for the information.


Inform the others what we know about our hand. This can be from what we have been told in the past and can in other peoples hands. For instance if I had a green five in my hand and was told I have a five and can account for all the other fives I would say I have a five and know the color.
If we have no or limited knowledge of our hands we sometimes will say if you tell me nothing I will discard from a certain side of my hand. This is used as a reminder that I have gotten no information about my hand lately and am assuming I have nothing but garbage. 


While some of those may be breaking the spirit of the game they do make it more enjoyable for the group we play in. It all depends on what your group wants to do.