Currently, it's not possible to make tl-select-profile and tl-check-antivirus display strings in the client language. This is because the tl-set-clientlang.sh script runs from xstartup.d, but xstartup.d has not been executed before these programs. Perhaps we should fix this somehow; perhaps tl-select-profile and tl-check-antivirus should read the client_lang capabilities directly.
This bug is basically solved, not that tl-select-profile etc are executed from xstartup.d rather than being hardcoded into xstartup. It should suffice just to add a link to tl-set-clientlang.sh with a number lower than the script that you want translated. At this point, however, tl-set-clientlang.sh is not linked by default.
As noted in the previous comment, most things will be translated as long as client lang is set early in xstartup.d. The big remaining problem is tl-run-xstartup-feedback which is started before anything in xstartup.d is executed.
