I can't sit cross legged...
no problem - you can still do yoga and meditation.
Yoga, which includes meditation as one of it's tools, is there as a practise to fit you and not the other way.
You might find that blocks, meditation stools, Zafu cushions or chairs work well for you depending on your knees, ankles, hips - we will assess this during the class and find the comfortable position for you.
As long as you can sit upright and are comfortable, you have the perfect yoga pose for meditation and breathing practises; whether the legs are crossed or otherwise is unimportant.