Is Beer-Lambert law also valid for fluorescence and luminescence?
No the Beer Lambert law  ($I_{trans}=I_0\exp(-\epsilon[C]L)$) does not apply as this shows that the transmitted light intensity decreases exponentially with concentration as it passes through a solution. 

Fluorescence/luminescence is directly proportional to the concentration of molecules excited provided that the solution  is dilute so that dimers or excimers are not formed and that self-absorption of the fluorescence light by another part of the same solution does not occur.