Should I mix weight lifting with cardio?

The short answer is yes! Strength training and cardio work better together than they do apart.

It may surprise you, but doing cardio can help you build muscle.

How?

A healthy cardiovascular system helps your body recover between sets of heavy lifts. It also helps your body recover between intense training sessions. If you can recover better between sets and sessions, you can increase your training volume and training quality, which will lead to muscle and strength gains.

Additionally, lifting weights can make you a better cardio athlete.

How?

Well programmed strength training addresses muscle imbalances and reduces risk of injuries, which means you can train more often and miss fewer workouts. It also increases your potential power output, which is one of the best measures of over all athletic performance. 

How much strength training you need vs how much cardio you should do all depends on your goals, and that is where good coaching and programming come in.