Road Bike Hire Eastern Scotland

Might be worth a look at Spinlister.

I've rented a bike from Biketrax in Edinburgh before - decent selection of bikes but pricey (if you wanted to rent for the whole month it would be cheaper to buy the bike new!) You might find somewhere a bit cheaper, but I suspect any commerical bike hire won't be cost effective for such a long time period. You might be better off trying to buy a second hand bike and sell it on at the end of the month? Or making contact with local cycling groups and see if anyone has one they would be willing to lend you?

I have bought but not rented from here: https://www.biketrax.co.uk/hire/ and they are good people with proper road and gravel bikes. Rental will be more expensive than many holiday destinations because bikes lead a harder life here than in sunny places.

If you decide to buy a used bike for the month there are sometimes good things at the Bike Station in Edinburgh - it's a charity that refurbs donated bikes. Prices are keen but stock very variable. You might just get something rideable for less than a month's rental charges, but don't expect modern or fancy stuff.

I agree with Chris, East Lothian is a good place to ride - plenty of quiet roads, coastal views, decent hills and good cafés, in particular the Old Smiddy at Tyninghame, the Lanterne Rouge in Gifford and Falko in Haddington. Cake is the main focus of my riding.

If you are into hills then take a look at Redstone Rig and Crystal Rig, two stingers quite close to each other.

You will need an eye for a pothole and a waterproof jacket - the Edinburgh festival starts at the beginning of August and torrential rain is guaranteed. And bizarrely, even in summer the local weather can be pretty cold on the coast and warm in the hills.

There are a few Edinburgh-based folk here. I haven't rented myself in Edinburgh so no particular recommendations.  (Unless you fancied turning to the dark side in which case you want Laid back bikes).  There's a page with some old (but recently updated) rental notes here - there's also lots of other local info there.

Also - maybe worth posting on CityCyclingEdinburgh forum?

I'm assuming you're coming in to Edinburgh.  Obviously there will be no problems renting bikes and purchasing cycle clothing in town.  Transport around the region is pretty good on the railways.  In the Scottish central belt you don't generally need to book bikes on trains and most local Scotrail ones come with two or four bike spaces.  It is first come-first served but unless there's some event on you should be OK.  If you went a bit further it is worth booking although that can be a pain as you have to deal with the individual train companies.  There is also one route with bike-carrying buses - though not all of them do.

East Lothian and around has some great riding!  If you're old school and like physical maps I recommend getting a Spokes map for East Lothian - they've ones covering the region.