In theory, you have the right to use your HL anywhere you want. In practice, however, it is not as obvious and clear-cut. Your employer, for example, by law cannot tell you not to use your HL while at work unless it interferes with your job. If the business has a clear cut policy of English-only, they are required to inform you of the policy and consequences if the policy is not followed.
However, given the volatile nature of immigration crackdowns and profiling based, among other things, on the language an individual is using, you should keep in mind that not all laws are observed as they were intended.