Is it deer resistant?

Yes

Mexican Sunflower is deer resistant.

Tithonia rotundifolia

Deer: Rarely
Height: 6 ft (1.8 m)
Spread: 3 ft (91 cm)
Zones: 2–12
Light: Full sun

Annual
Biennial

Mexican Sunflower (Tithonia rotundifolia)

Photo: Jonathan Billinger · CC BY-SA 2.0

Annual Tithonia

More details

Light: Full sun
Water: Low, Medium
Type: Annual, Biennial
Maintenance: Low
Growth: Fast
Bloom: Fall, Summer
Features: Drought tolerant, Flowering
Best uses: Border, Patio, Poolside