my itinerary! what you think?

Hi leaving in feb with my girlfriend, backpacking around the world.

leave UK and head to bangkok (3 nights)
Bangkok to phuket (includes time at patong, karon and 4 days on Phi phi don)
Phuket to Singapore (3 nights)
Singapore to sydney (city sights, beaches, blue mountains)
make way up the east coast calling in byron bay, noosa, airlie beach, whitsundays, etc) about 15-20 days
to cairns (4 days - barrier reef and daintree)
fly from carins to alice springs (3 nights) take in tour to ayers rock and alice springs
fly from alicesprings to adelaide ( 4 nights in adelaide)
adventuretours trip from adelaide to melbourne ( ocean road etc)
5 nights in melbourne
adventure tours trip from melbourne to sydney (3 days)
2 days in sydney to rest/chill and to visit places we missed first time in sydney
then fly from sydney to oahu, hawaii (8 nights)
oahu to san fran ( 7 nights inc day tour to yosemite and big sur etc, redwoods)
amtrak train from san fran to LA (staying in santa monica ) 4 days - sights and theme park etc
LA to Vegas (4 days inc day tour to grand canyon)
VEgas to san diego (4 days)
flight san diego to Cancun ( 12 days in mexico - 4 in cancun 8 in playa del carmen, seeing tulum, puerto morelos, isla mujeres etc, chichen itza)
flight cancun to toronto (4 days - day trip to niagara falls)
bus to New York (6 nights)
bus to washington DC (4 nights)

Flight back to UK! i think its about 130 days altogether! done loads fo research and plces to visit at each city/place etc, but more advice always welcome especially on any great hostels/hidden gems etc

what you all think!? i cant wait already, leaving in 18 weeks! ha

ive done loads of research

Quoting silverteen

ive done loads of research

I can tell. I think the whole itinerary might be over-researched, though. It feels to me like you're trying to cram too many experiences into a time frame which won't really hold them comfortably. For example, you're doing both the entire east coast, and the middle of Australia in... what? 45 days? People frequently take half a year for that loop. Same for the "day tours" you want to take to Yosemite and Big Sur; those are places which need several days to just slowly experience, not things which should be seen in a 15 minute photo-opportunity before needing to cram back into the bus again.
You also seem to lack any leftover time for recovering / relaxing (long-term travel / always being on the move is exhausting), or doing off-the-cuff sidetrips as you get inspired for them by travellers you meet on the road.
If you can and haven't booked everything already, I'd go and cut some destinations from this itinerary (or stretch it over a longer period of time). Then, for every two weeks of travel, I'd add 3 days of empty space with a big question mark next to it, to be filled in no earlier than during the two preceding weeks. Either spend it seeing a destination more in depth, or do a local side-trip. But I predict that most frequently, you'll take the opportunity to spend it sitting in the lounge of your hostel with a cup of tea and a book, grateful to be doing nothing at all and just having some quiet time together. Maybe going out at night to catch a movie, or climbing a local hill to watch a slow sunset.

The individual locations and activities you've planned for this trip all look good, though, insofar as I know them.

Your itinerary sounds impressive, but I agree with Sander about timing issues.

I've done the New York-Niagara Falls-Washington DC circuit a few years back, and after getting off the bus I certainly wasn't in the mood for sightseeing but rather chilling out and watch the world go by.

Your West coast circuit is similar to one of my past road trips and you seem to underestimate distances.
Is it really worth the time and money to say you've been to Yosemite for instance, however impressive the area is. You might wanna look into car rentals for this part of your travels, because for instance Big Sur is more or less half way between SF and LA and the coast is terrific.

I tend as well to research very much ahead, going even as far as creating my personal travelbooks now.
But I have no intention of doing everything I wrote down, and I decide no more than one day ahead what to go for.

One of my happiest memories of New York is sitting in Central Park for hours reading newspapers and drinking coffee.