It is really easy to get around and the buses are cheap and pretty modern. It is easy to get to know the friendly Mexicans and travellers alike and you can achieve a good balance of being on your own and being amongst people.

Accommodation for solo travellers:

Many use their lonely planet to find accommodation but Mexico is a great place for groups getting together who are wandering off in the same direction. You seem to have a choice of which person or people to follow which is great as you do feel safer when you are travelling with someone.

There are lots of choices of accommodation, hammocks and cabañas in the jungle
or on the beach, hotels with and without hot water and hostels which although aren't as clean or as modern as in Australia seemed to have more character.

Budget for solo travellers:

Mexican Pesos are around 21 to the £1 but accomodation can range from 3 pesos for a hammock to $60 USD for a Hotel on the east coast like Cancun and Playa del
Carmen which is full American tourists.

For a dorm in a hostel its around $6 USD and seems to be a good option for the cities. Mexico is large and mountainous so its better to get round at night so you don't miss too many days.

You can sleep on the bus and save money, however we wouldn't recommend travelling at night on your own.

Trips and activities for solos:

Well there is no shortage of things to do in Mexico and there are plenty of Ruins to see if you are into to that sort of thing.

Hostels organise lots of trips or you can get to many places on your own.

Here is a list of ideas.

Ruins
Pirámides de Teotihuacan, Mexico City
Palenque, in the jungle
Tulum, by the beach

Spanish language course and/or Mexican cooking
lessons, Oaxaca
Puerto Escondido, Beach
Zicatela, Surfing
San Cristobal de Las Casas, visit indigenous villages
Waterfall Misol-Ha, Chiapas
Cascades Aqua Azul, Chiapas

Markets - everywhere

I think the focus might be more on seeing things rather than doing activities but there are so many amazing things to see and understand about this country.

There are lots of lone travellers in Mexico and it is definitely an exciting place with lots to investigate that will help prepare you for venturing further down south.