This song is originally from 1976 and was one of my favorite songs that my family square danced to when I was a child. If you use other cha-cha type songs, ignore the tag/bridge.
STEP, LOCK, FORWARD SHUFFLE, ROCK, RECOVER, ½ TURN LEFT
1-2
Step forward with right foot, lock step left in behind right
3&4
Shuffle forward right, left, right (can be locked)
5-6
Rock forward with left foot, recover weight back to right foot
7&8
Shuffle left, right, left turning ½ left
SIDE ROCK, ¼ TURN LEFT, SHUFFLE FORWARD, CONTRA ROCK, RECOVER ¾ TURN RIGHT
1-2
Rock right foot to right side, turn ¼ left, recover weight forward to left foot
3-4
Shuffle forward right, left, right
5
Rock forward with left foot turning shoulders slightly left in a contra body position
6
Recover weight back to right foot, shoulders square
7
Step back with left foot, turning ¼ right (pull shoulder back as you go into the turn)
&
Turn ¼ right, step forward with right foot
8
Turn ¼ right, step side with left foot
As an easier variation of counts 5-8, do a regular rock forward with left foot, recover weight back to right foot, turn ¼ left, step left foot to left side, step together with right foot, step left foot to left side
CROSS ROCK, RECOVER, SIDE SHUFFLE RIGHT, CROSS ROCK, RECOVER, SHUFFLE ¼ TURN LEFT
1-2
Rock right foot across in front of left, recover weight back to left foot
3&4
Step right foot to right side, step together with left foot, step right foot to right side
5-6
Rock left foot across in front of right, recover weight back to right foot
7&8
Step left foot to left side, turning 1/8 left, step together with right, turn 1/8 left, step forward with left foot
There is a right count tag/bridge after the 5th, 6th, 11th and 12th repetitions. Rock forward right (1), recover weight back to left foot (2), rock back with right foot (3), recover weight forward to left foot (4). The easiest way to remember this is that at the beginning of each of those repetitions Marty Robbins is singing "El Paso City, by the Rio Grande" which is the chorus. Enjoy it and sing along!