To find \( p(2) - 1 \), we first need to calculate the characteristic polynomial of the matrix \( M \). The characteristic polynomial is given by the determinant of \( M - xI \), where \( I \) is the identity matrix and \( x \) is the variable. For this matrix, we calculate the determinant of \( M - 2I \), substitute \( x = 2 \) into the resulting polynomial, and subtract 1 to obtain the value \( p(2) - 1 = 31 \).
Thus, the correct answer is 31.