The results are:
- The probability of exactly 5 Mexican-Americans among 12 jurors is \( P(x=5) = 0.0073 \).
- The probability of 5 or fewer Mexican-Americans among 12 jurors is \( P(x \leq 5) = 0.0089 \).
Thus, the final answers are:
\[
\boxed{P(x=5) = 0.0073}
\]
\[
\boxed{P(x \leq 5) = 0.0089}
\]