Yes, in the towns and key sites. You will have strong 4G/LTE in Santiago and all major cities.
- Patagonia: You will have good 4G in the towns of Puerto Natales and Punta Arenas. Inside Torres del Paine National Park, you will have a signal at the park entrances and main lodges/campsites (like Paine Grande), but not on the remote hiking trails (like the W Trek).
- Atacama: You will have excellent 4G in the town of San Pedro de Atacama, but you will lose signal on the high-altitude tours to the geysers or remote salt flats.