If you have true stucco (a finish applied over a wood frame) you will fall under the "wood" rate, not the "mixed" rate.
"Mixed" will apply if you have (I think) 50% of the structure being of concrete.
Different companies have different rates and also different levels of reliability.
Read your policy well so that you know exactly what your coverage is - and note that there are substantial penalties for under-insuring.
Every year the costs tend to go up a bit, but in general I think it's around $11 per $1,000 (1%) for all concrete and around $30 per $1,000 (3%)for all wood.