In general, the individual liberties set out in the Bill of Rights apply broadly to all people, in all their interactions with the US government. The Bill of Rights does not use the word "citizen," but does in several places use the broader term "person." For example,
> No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a grand jury, except in cases arising in the land or naval forces, or in the militia, when in actual service in time of war or public danger;
It also uses the phrase, "the people." For example, in the 4th Amendment,
> The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
In the case of the 1st Amendment, which concerns freedom of speech/religion/the press, it appears to be a general prohibition on government interference with freedom of speech, with no specification of whose freedom of speech is meant:
> Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the government for a redress of grievances.