Quick answer
Mueller is my leading Austin recommendation for someone moving alone. Its parks, trails, restaurants, community activities, and recurring events create social opportunities through the neighborhood itself rather than relying only on apartment amenities. Downtown offers the greatest concentration of nightlife, music, restaurants, and events, but its pricing excludes many recent graduates. South Congress is highly active and walkable, while South Lamar offers restaurants, music, and access to Zilker Park. Riverside is better understood as a value location near those social areas than as a leading social neighborhood by itself. Workplace, budget, and preferred pace should determine the final choice.
Explore related apartment guides and city and neighborhood information. Rental prices, availability, office locations and incentives can change; confirm time-sensitive details before making a decision.