You call the shots about taking a plea. Your attorney can only advise you. Of course you can speak with your co-defendant. However, if your interests do not coincide (eg. - you point the finger at each other), then it may not be a good idea. Also, you can not intimidate anyone or induce someone to give false testimony, which I'm sure you already know.
If you are not happy with your attorney, make an application to the court for a new court-appointed attorney, or better yet hire a private attorney.
Mr. Kennedy provided a fine answer, and I will just add one bit: Here in Washington co-defendants are often court ordered from having contact with one another during the case. You might want to check your original conditions of release or whether there is a no-contact order in place. You wouldn't want to incriminate yourself regarding a separate crime (violation of the no-contact order, if one exists).